Condensed Consolidated Balance Sheets - USD ($)	Nov. 30, 2017	May 31, 2017
Current assets:
Cash and cash equivalents	$ 1,713,326	$ 3,324,934
Short-term investments	1,030,530	1,022,326
Accounts receivable, net	3,508,985	2,545,773
Inventory	11,790,428	11,488,610
Costs and estimated earnings in excess of billings	7,519,111	6,868,393
Other current assets	308,959	427,478
Total current assets	25,871,339	25,677,514
Maintenance and other inventory, net	842,153	878,779
Property and equipment, net	10,224,380	9,994,716
Other assets	183,312	180,579
Deferred income taxes	429,115	429,115
Total assets	37,550,299	37,160,703
Current liabilities:
Accounts payable	1,340,926	1,329,321
Accrued commissions	1,105,414	846,941
Billings in excess of costs and estimated earnings	793,072	1,295,989
Other current liabilities	919,483	832,060
Total current liabilities	4,158,895	4,304,311
Stockholders' Equity:
Common stock and additional paid-in capital	9,351,159	9,170,041
Retained earnings	26,869,604	26,515,710
Stockholders’ equity before treasury stock	36,220,763	35,685,751
Treasury stock -  at cost	(2,829,359)	(2,829,359)
Total stockholders’ equity	33,391,404	32,856,392
Total liabilities and stockholders’ equity	$ 37,550,299	$ 37,160,703