Condensed Consolidated Statement of Cash Flows - USD ($)	3 Months Ended
	Aug. 31, 2021	Aug. 31, 2020
Operating activities:
Net income	$ 181,877	$ 176,011
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation	313,785	289,485
Stock options issued for services		49,717
Changes in other assets and liabilities:
Accounts and other receivables	1,364,269	1,110,640
Inventory	387,855	345,341
Costs and estimated earnings in excess of billings	(1,787,856)	77,580
Other current assets	64,164	(3,342)
Accounts payable	158,458	(242,929)
Accrued commissions	191,105	139,753
Billings in excess of costs and estimated earnings	(394,560)	(627,244)
Other current liabilities	(449,897)	(807,885)
Net operating activities	29,200	507,127
Investing activities:
Acquisition of property and equipment	(461,953)	(244,458)
Other investing activities	(5,848)	(7,233)
Net investing activities	(467,801)	(251,691)
Financing activities:
Proceeds from issuance of common stock, net	3,833	3,738
Net change in cash and cash equivalents	(434,768)	259,174
Cash and cash equivalents - beginning	20,581,604	15,159,827
Cash and cash equivalents - ending	$ 20,146,836	$ 15,419,001