Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Nov. 30, 2020	Nov. 30, 2019
Operating activities:
Net income	$ 821,301	$ 1,271,583
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation	590,643	560,796
Stock options issued for services	49,717	55,437
Debt forgiveness	(1,461,500)
Changes in other assets and liabilities:
Accounts receivable	997,255	(1,068,375)
Inventory	989,304	414,317
Costs and estimated earnings in excess of billings	211,872	4,522,075
Other current assets	(22,710)	236,465
Accounts payable	(491,400)	528,564
Accrued commissions	20,545	(462,187)
Billings in excess of costs and estimated earnings	(355,686)	1,687,557
Other current liabilities	(787,431)	(379,028)
Net operating activities	561,910	7,367,204
Investing activities:
Acquisition of property and equipment	(720,856)	(317,421)
Other investing activities	(14,721)	(7,116)
Net investing activities	(735,577)	(324,537)
Financing activities:
Proceeds from issuance of common stock, net	7,381	6,853
Net change in cash and cash equivalents	(166,286)	7,049,520
Cash and cash equivalents - beginning	15,159,827	5,071,822
Cash and cash equivalents - ending	$ 14,993,541	$ 12,121,342