<?xml version="1.0" encoding="us-ascii"?>
<!-- Created by Merrill Corporation -->
<!-- Generated by Fujitsu Interstage XWand B0166_M01 -->
<!--Generated by IRIS XBRL Generation Engine-->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink">
  <link:roleRef roleURI="http://www.pxt.franklinstreetproperties.com/role/BalanceSheet" xlink:type="simple" xlink:href="pxt-20120930.xsd#BalanceSheet" />
  <link:roleRef roleURI="http://www.pxt.franklinstreetproperties.com/role/StatementOfIncome" xlink:type="simple" xlink:href="pxt-20120930.xsd#StatementOfIncome" />
  <link:roleRef roleURI="http://www.pxt.franklinstreetproperties.com/role/CashFlows" xlink:type="simple" xlink:href="pxt-20120930.xsd#CashFlows" />
  <link:calculationLink xlink:type="extended" xlink:role="http://www.pxt.franklinstreetproperties.com/role/BalanceSheet">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_Assets" xlink:label="Assets" xlink:title="Assets" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RealEstateInvestmentPropertyNet" xlink:label="RealEstateInvestmentPropertyNet" xlink:title="RealEstateInvestmentPropertyNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="RealEstateInvestmentPropertyNet" xlink:title="calculation: Assets to RealEstateInvestmentPropertyNet" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RealEstateInvestmentPropertyAtCost" xlink:label="RealEstateInvestmentPropertyAtCost" xlink:title="RealEstateInvestmentPropertyAtCost" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="RealEstateInvestmentPropertyNet" xlink:to="RealEstateInvestmentPropertyAtCost" xlink:title="calculation: RealEstateInvestmentPropertyNet to RealEstateInvestmentPropertyAtCost" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_Land" xlink:label="Land" xlink:title="Land" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="RealEstateInvestmentPropertyAtCost" xlink:to="Land" xlink:title="calculation: RealEstateInvestmentPropertyAtCost to Land" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentBuildingAndBuildingImprovements" xlink:label="InvestmentBuildingAndBuildingImprovements" xlink:title="InvestmentBuildingAndBuildingImprovements" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="RealEstateInvestmentPropertyAtCost" xlink:to="InvestmentBuildingAndBuildingImprovements" xlink:title="calculation: RealEstateInvestmentPropertyAtCost to InvestmentBuildingAndBuildingImprovements" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FixturesAndEquipmentGross" xlink:label="FixturesAndEquipmentGross" xlink:title="FixturesAndEquipmentGross" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="RealEstateInvestmentPropertyAtCost" xlink:to="FixturesAndEquipmentGross" xlink:title="calculation: RealEstateInvestmentPropertyAtCost to FixturesAndEquipmentGross" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation" xlink:label="RealEstateInvestmentPropertyAccumulatedDepreciation" xlink:title="RealEstateInvestmentPropertyAccumulatedDepreciation" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="RealEstateInvestmentPropertyNet" xlink:to="RealEstateInvestmentPropertyAccumulatedDepreciation" xlink:title="calculation: RealEstateInvestmentPropertyNet to RealEstateInvestmentPropertyAccumulatedDepreciation" order="2.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="FiniteLivedIntangibleAssetsNet" xlink:title="FiniteLivedIntangibleAssetsNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="FiniteLivedIntangibleAssetsNet" xlink:title="calculation: Assets to FiniteLivedIntangibleAssetsNet" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="pxt-20120930.xsd#pxt_OffMarketLeaseFavorableNet" xlink:label="OffMarketLeaseFavorableNet" xlink:title="OffMarketLeaseFavorableNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="OffMarketLeaseFavorableNet" xlink:title="calculation: Assets to OffMarketLeaseFavorableNet" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="CashAndCashEquivalentsAtCarryingValue" xlink:title="CashAndCashEquivalentsAtCarryingValue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="CashAndCashEquivalentsAtCarryingValue" xlink:title="calculation: Assets to CashAndCashEquivalentsAtCarryingValue" order="4.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccountsReceivableNet" xlink:label="AccountsReceivableNet" xlink:title="AccountsReceivableNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="AccountsReceivableNet" xlink:title="calculation: Assets to AccountsReceivableNet" order="5.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DeferredRentReceivablesNet" xlink:label="DeferredRentReceivablesNet" xlink:title="DeferredRentReceivablesNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="DeferredRentReceivablesNet" xlink:title="calculation: Assets to DeferredRentReceivablesNet" order="6.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DeferredCostsLeasingNet" xlink:label="DeferredCostsLeasingNet" xlink:title="DeferredCostsLeasingNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="DeferredCostsLeasingNet" xlink:title="calculation: Assets to DeferredCostsLeasingNet" order="7.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssets" xlink:label="PrepaidExpenseAndOtherAssets" xlink:title="PrepaidExpenseAndOtherAssets" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Assets" xlink:to="PrepaidExpenseAndOtherAssets" xlink:title="calculation: Assets to PrepaidExpenseAndOtherAssets" order="8.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="LiabilitiesAndStockholdersEquity" xlink:title="LiabilitiesAndStockholdersEquity" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_Liabilities" xlink:label="Liabilities" xlink:title="Liabilities" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="LiabilitiesAndStockholdersEquity" xlink:to="Liabilities" xlink:title="calculation: LiabilitiesAndStockholdersEquity to Liabilities" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent" xlink:label="AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent" xlink:title="AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Liabilities" xlink:to="AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent" xlink:title="calculation: Liabilities to AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SecurityDepositLiability" xlink:label="SecurityDepositLiability" xlink:title="SecurityDepositLiability" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Liabilities" xlink:to="SecurityDepositLiability" xlink:title="calculation: Liabilities to SecurityDepositLiability" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DueToAffiliateCurrentAndNoncurrent" xlink:label="DueToAffiliateCurrentAndNoncurrent" xlink:title="DueToAffiliateCurrentAndNoncurrent" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Liabilities" xlink:to="DueToAffiliateCurrentAndNoncurrent" xlink:title="calculation: Liabilities to DueToAffiliateCurrentAndNoncurrent" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OffMarketLeaseUnfavorable" xlink:label="OffMarketLeaseUnfavorable" xlink:title="OffMarketLeaseUnfavorable" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Liabilities" xlink:to="OffMarketLeaseUnfavorable" xlink:title="calculation: Liabilities to OffMarketLeaseUnfavorable" order="4.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="StockholdersEquity" xlink:title="StockholdersEquity" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="LiabilitiesAndStockholdersEquity" xlink:to="StockholdersEquity" xlink:title="calculation: LiabilitiesAndStockholdersEquity to StockholdersEquity" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="PreferredStockValue" xlink:title="PreferredStockValue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="StockholdersEquity" xlink:to="PreferredStockValue" xlink:title="calculation: StockholdersEquity to PreferredStockValue" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CommonStockValue" xlink:label="CommonStockValue" xlink:title="CommonStockValue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="StockholdersEquity" xlink:to="CommonStockValue" xlink:title="calculation: StockholdersEquity to CommonStockValue" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="AdditionalPaidInCapital" xlink:title="AdditionalPaidInCapital" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="StockholdersEquity" xlink:to="AdditionalPaidInCapital" xlink:title="calculation: StockholdersEquity to AdditionalPaidInCapital" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccumulatedDistributionsInExcessOfNetIncome" xlink:label="AccumulatedDistributionsInExcessOfNetIncome" xlink:title="AccumulatedDistributionsInExcessOfNetIncome" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="StockholdersEquity" xlink:to="AccumulatedDistributionsInExcessOfNetIncome" xlink:title="calculation: StockholdersEquity to AccumulatedDistributionsInExcessOfNetIncome" order="4.0" weight="-1" />
  </link:calculationLink>
  <link:calculationLink xlink:type="extended" xlink:role="http://www.pxt.franklinstreetproperties.com/role/StatementOfIncome">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="NetIncomeLoss" xlink:title="NetIncomeLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="OperatingIncomeLoss" xlink:title="OperatingIncomeLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetIncomeLoss" xlink:to="OperatingIncomeLoss" xlink:title="calculation: NetIncomeLoss to OperatingIncomeLoss" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_Revenues" xlink:label="Revenues" xlink:title="Revenues" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="OperatingIncomeLoss" xlink:to="Revenues" xlink:title="calculation: OperatingIncomeLoss to Revenues" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RealEstateRevenueNet" xlink:label="RealEstateRevenueNet" xlink:title="RealEstateRevenueNet" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="Revenues" xlink:to="RealEstateRevenueNet" xlink:title="calculation: Revenues to RealEstateRevenueNet" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CostsAndExpenses" xlink:label="CostsAndExpenses" xlink:title="CostsAndExpenses" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="OperatingIncomeLoss" xlink:to="CostsAndExpenses" xlink:title="calculation: OperatingIncomeLoss to CostsAndExpenses" order="2.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CostOfRealEstateRevenue" xlink:label="CostOfRealEstateRevenue" xlink:title="CostOfRealEstateRevenue" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="CostsAndExpenses" xlink:to="CostOfRealEstateRevenue" xlink:title="calculation: CostsAndExpenses to CostOfRealEstateRevenue" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RealEstateTaxesAndInsurance" xlink:label="RealEstateTaxesAndInsurance" xlink:title="RealEstateTaxesAndInsurance" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="CostsAndExpenses" xlink:to="RealEstateTaxesAndInsurance" xlink:title="calculation: CostsAndExpenses to RealEstateTaxesAndInsurance" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:label="DepreciationAndAmortization" xlink:title="DepreciationAndAmortization" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="CostsAndExpenses" xlink:to="DepreciationAndAmortization" xlink:title="calculation: CostsAndExpenses to DepreciationAndAmortization" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InterestExpense" xlink:label="InterestExpense" xlink:title="InterestExpense" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="CostsAndExpenses" xlink:to="InterestExpense" xlink:title="calculation: CostsAndExpenses to InterestExpense" order="4.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="InvestmentIncomeInterest" xlink:title="InvestmentIncomeInterest" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetIncomeLoss" xlink:to="InvestmentIncomeInterest" xlink:title="calculation: NetIncomeLoss to InvestmentIncomeInterest" order="2.0" weight="1" />
  </link:calculationLink>
  <link:calculationLink xlink:type="extended" xlink:role="http://www.pxt.franklinstreetproperties.com/role/CashFlows">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInContinuingOperations" xlink:label="NetCashProvidedByUsedInContinuingOperations" xlink:title="NetCashProvidedByUsedInContinuingOperations" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:label="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:title="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInContinuingOperations" xlink:to="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:title="calculation: NetCashProvidedByUsedInContinuingOperations to NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="NetIncomeLoss" xlink:title="NetIncomeLoss" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="NetIncomeLoss" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to NetIncomeLoss" use="optional" order="1.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="DepreciationDepletionAndAmortization" xlink:title="DepreciationDepletionAndAmortization" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="DepreciationDepletionAndAmortization" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to DepreciationDepletionAndAmortization" use="optional" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="pxt-20120930.xsd#pxt_AmortizationFavorableRealEstateLeases" xlink:label="AmortizationFavorableRealEstateLeases" xlink:title="AmortizationFavorableRealEstateLeases" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="AmortizationFavorableRealEstateLeases" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to AmortizationFavorableRealEstateLeases" use="optional" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="pxt-20120930.xsd#pxt_AmortizationUnfavorableRealEstateLeases" xlink:label="AmortizationUnfavorableRealEstateLeases" xlink:title="AmortizationUnfavorableRealEstateLeases" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="AmortizationUnfavorableRealEstateLeases" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to AmortizationUnfavorableRealEstateLeases" use="optional" order="4.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts" xlink:label="ProvisionForDoubtfulAccounts" xlink:title="ProvisionForDoubtfulAccounts" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="ProvisionForDoubtfulAccounts" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to ProvisionForDoubtfulAccounts" use="optional" order="5.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="IncreaseDecreaseInAccountsReceivable" xlink:title="IncreaseDecreaseInAccountsReceivable" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInAccountsReceivable" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to IncreaseDecreaseInAccountsReceivable" use="optional" order="6.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StraightLineRent" xlink:label="StraightLineRent" xlink:title="StraightLineRent" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="StraightLineRent" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to StraightLineRent" use="optional" order="7.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:title="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" use="optional" order="8.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:label="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:title="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" use="optional" order="9.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInSecurityDeposits" xlink:label="IncreaseDecreaseInSecurityDeposits" xlink:title="IncreaseDecreaseInSecurityDeposits" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInSecurityDeposits" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to IncreaseDecreaseInSecurityDeposits" use="optional" order="10.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredLeasingFees" xlink:label="IncreaseDecreaseInDeferredLeasingFees" xlink:title="IncreaseDecreaseInDeferredLeasingFees" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInDeferredLeasingFees" xlink:title="calculation: NetCashProvidedByUsedInOperatingActivitiesContinuingOperations to IncreaseDecreaseInDeferredLeasingFees" use="optional" order="11.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:label="NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:title="NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInContinuingOperations" xlink:to="NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:title="calculation: NetCashProvidedByUsedInContinuingOperations to NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" order="2.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsToAcquireRealEstate" xlink:label="PaymentsToAcquireRealEstate" xlink:title="PaymentsToAcquireRealEstate" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:to="PaymentsToAcquireRealEstate" xlink:title="calculation: NetCashProvidedByUsedInInvestingActivitiesContinuingOperations to PaymentsToAcquireRealEstate" order="1.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:label="NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:title="NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInContinuingOperations" xlink:to="NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:title="calculation: NetCashProvidedByUsedInContinuingOperations to NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" order="3.0" weight="1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStock" xlink:label="PaymentsOfDividendsPreferredStockAndPreferenceStock" xlink:title="PaymentsOfDividendsPreferredStockAndPreferenceStock" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:to="PaymentsOfDividendsPreferredStockAndPreferenceStock" xlink:title="calculation: NetCashProvidedByUsedInFinancingActivitiesContinuingOperations to PaymentsOfDividendsPreferredStockAndPreferenceStock" order="1.0" weight="-1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInDueToRelatedParties" xlink:label="IncreaseDecreaseInDueToRelatedParties" xlink:title="IncreaseDecreaseInDueToRelatedParties" />
    <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:to="IncreaseDecreaseInDueToRelatedParties" xlink:title="calculation: NetCashProvidedByUsedInFinancingActivitiesContinuingOperations to IncreaseDecreaseInDueToRelatedParties" order="2.0" weight="1" />
  </link:calculationLink>
</link:linkbase>
