Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019
Operating activities:
Net income	$ 176,011	$ 354,577
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation	289,485	280,398
Stock options issued for services	49,717	55,437
Changes in other assets and liabilities:
Accounts receivable	1,110,640	(1,567,219)
Inventory	345,341	(36,615)
Costs and estimated earnings in excess of billings	77,580	3,073,202
Other current assets	(3,342)	43,497
Accounts payable	(242,929)	3,327
Accrued commissions	139,753	(305,388)
Billings in excess of costs and estimated earnings	(627,244)	(398,423)
Other current liabilities	(807,885)	231,251
Net operating activities	507,127	1,734,044
Investing activities:
Acquisition of property and equipment	(244,458)	(72,919)
Other investing activities	(7,233)	(5,685)
Net investing activities	(251,691)	(78,604)
Financing activities:
Proceeds from issuance of common stock, net	3,738	3,377
Net change in cash and cash equivalents	259,174	1,658,817
Cash and cash equivalents - beginning	15,159,827	5,071,822
Cash and cash equivalents - ending	$ 15,419,001	$ 6,730,639