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Inventories
3 Months Ended
Jul. 31, 2013
Inventory Disclosure [Abstract]  
Inventories
Inventories 
We use the last-in, first-out (“LIFO”) method to determine the cost of most of our inventories.  If the LIFO method had not been used, inventories at current cost would have been $209 million higher than reported as of April 30, 2013, and $212 million higher than reported as of July 31, 2013.  Changes in the LIFO valuation reserve for interim periods are based on a proportionate allocation of the estimated change for the entire fiscal year.