STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
OPERATING ACTIVITIES
Net income	$ 17,124,699	$ 22,694,458
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation	308,147	196,738
Bond premium (discount) amortization	(106,354)	60,868
Provision for current estimate of credit losses	9,514	0
Stock-based compensation	141,936	59,657
Deferred income taxes	(1,003,844)	161,894
Changes in operating assets and liabilities
Accounts receivable	3,368,997	(1,818,515)
Inventories	(741,575)	(1,328,375)
Prepaid expenses and other assets	110,043	(208,532)
Accounts payable and accrued expenses	(964,152)	(726,695)
Net cash provided by operating activities	18,247,411	19,091,498
INVESTING ACTIVITIES
Purchases of fixed assets	(16,731)	(935,791)
Purchases of marketable securities	(6,103,185)	(28,441,317)
Proceeds from maturities of marketable securities	15,700,000	20,750,000
Receipt of tenant improvement allowance	0	100,000
Net cash provided by (used in) investing activities	9,580,084	(8,527,108)
FINANCING ACTIVITIES
Exercise of stock options, net of shares withheld for exercise price	117,463	(3)
Repurchase of common stock	0	(20,697)
Payment of dividends to shareholders	(19,331,304)	(19,323,304)
Net cash used in financing activities	(19,213,841)	(19,344,004)
Increase (decrease) in cash and cash equivalents	8,613,654	(8,779,614)
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance	1,669,896	10,449,510
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	10,283,550	1,669,896
Supplemental disclosures of cash flow information
Cash paid during the year for income taxes	$ 4,539,071	$ 4,501,656