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Note 3 – Marketable Securities (Tables)
 3 Months Ended
Jul. 31, 2022
Investments, Debt and Equity Securities [Abstract]  
[custom:ScheduleOfAmortizedCostNetUnrealizedGainLossFairValues]
   Cost  Unrealized Gains (Losses)  Fair Value
Asset-backed securities  $2,504,563   $(35,324)  $2,469,239 
Corporate bonds   35,544,776    (1,305,388)   34,239,388 
Total  $38,049,339   $(1,340,712)  $36,708,627 
[custom:ScheduleOfContractualMaturitiesFairValueMeasurements]
   One Year or Less  One to
Five Years		  Over Five Years  Total
Asset-backed securities  $—     $2,469,239   $—     $2,469,239 
Corporate bonds   16,876,795    16,804,473    558,120    34,239,388 
Total  $16,876,795   $19,273,712   $558,120   $36,708,627 
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
   Level 1  Level 2  Level 3  Total
Asset-backed securities  $—     $2,469,239   $—     $2,469,239 
Corporate bonds   —      34,239,388    —      34,239,388 
Total  $—     $36,708,627   $—     $36,708,627