Balance Sheets (Unaudited) - USD ($)	Nov. 30, 2016	May 31, 2016
Current assets:
Cash and cash equivalents	$ 4,015,826	$ 6,086,080
Short-term investments	1,014,246	1,000,000
Accounts receivable, net	3,783,449	3,992,214
Inventory	10,576,467	9,604,956
Costs and estimated earnings in excess of billings	6,424,624	5,500,771
Other current assets	1,273,040	1,437,381
Total current assets	27,087,652	27,621,402
Maintenance and other inventory, net	609,545	697,043
Property and equipment, net	9,777,753	8,994,504
Other assets	178,128	175,350
Total Assets	37,653,078	37,488,299
Current liabilities:
Accounts payable	2,041,703	1,767,017
Accrued commissions	898,572	683,600
Billings in excess of costs and estimated earnings	838,417	1,463,621
Other current liabilities	1,656,329	2,733,847
Total current liabilities	5,435,021	6,648,085
Long-term liabilities	682,985	682,985
Stockholders' Equity:
Common stock and additional paid-in capital	9,003,309	8,628,280
Retained earnings	25,333,247	24,185,133
Treasury stock - at cost	(2,801,484)	(2,656,184)
Total stockholders’ equity	31,535,072	30,157,229
Total liabilities and shareholders’ equity	$ 37,653,078	$ 37,488,299

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.