Note 3 – Fair Value Measurements (Tables)

6 Months Ended

Oct. 31, 2021

Fair Value Disclosures [Abstract]

[custom:ScheduleOfAmortizedCostNetUnrealizedGainLossFairValues]

	Amortized Cost		Net Unrealized Gains (Losses)			Fair Value
Money market funds	$	1,598,428	$	732		$	1,599,160
Asset-backed securities		3,444,037		(9,081	)		3,434,956
Corporate bonds		43,219,180		(130,639	)		43,088,541
Total	$	48,261,645	$	(138,988	)	$	48,122,657

[custom:ScheduleOfContractualMaturitiesFairValueMeasurements]

	One Year or Less		Over One Year		Over Five Years		Total
Money market funds	$	1,599,160	$	—	$	—	$	1,599,160
Asset-backed securities		—		3,434,956		—		3,434,956
Corporate bonds		14,575,236		27,911,550		601,755		43,088,541
Total	$	16,174,396	$	31,346,506	$	601,755	$	48,122,657

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Level 1		Level 2		Level 3		Total
Money market funds	$	1,599,160	$	—	$	—	$	1,599,160
Asset-backed securities		—		3,434,956		—		3,434,956
Corporate bonds		—		43,088,541		—		43,088,541
Total	$	1,599,160	$	46,523,497	$	—	$	48,122,657