Earnings Per Share And Stockholders' Equity (Computation Of Basic And Diluted Earnings (Loss) Per Share) (Details) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Earnings Per Share And Stockholders' Equity [Abstract]
Net income (loss)	$ 626,858	$ (900,666)	$ 661,183	$ 361,025	$ (273,808)	$ 1,022,208
Weighted-average shares, Basic	4,257,508		4,242,508		4,254,247	4,242,196
Weighted-average shares, Effect of dilutive stock options			36,393			9,394
Diluted	4,257,508		4,278,901		4,254,247	4,251,590
Basic earnings (loss) per share	$ 0.15		$ 0.16		$ (0.06)	$ 0.24
Diluted earnings (loss) per share	$ 0.15		$ 0.15		$ (0.06)	$ 0.24