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Note 3 – Marketable Securities (Tables)
 9 Months Ended
Jan. 31, 2023
Investments, Debt and Equity Securities [Abstract]  
[custom:ScheduleOfAmortizedCostNetUnrealizedGainLossFairValues]
   Cost  Unrealized Gains (Losses)  Fair Value
Asset-backed securities  $924,509   $(14,218)  $910,291 
Corporate bonds   20,951,812    (1,132,070)   19,819,742 
Total  $21,876,321   $(1,146,288)  $20,730,033 
[custom:ScheduleOfContractualMaturitiesFairValueMeasurements]
   One Year or Less  One to Three Years  Three to Five Years  Total
Asset-backed securities  $ —     $910,291   $ —     $910,291 
Corporate bonds   6,494,035    12,744,060    581,647    19,819,742 
Total  $6,494,035   $13,654,351   $581,647   $20,730,033 
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
   Level 1  Level 2  Level 3  Total
Asset-backed securities  $ —     $910,291   $ —     $910,291 
Corporate bonds    —      19,819,742     —      19,819,742 
Total  $ —     $20,730,033   $ —     $20,730,033