Quarterly report pursuant to Section 13 or 15(d)

The estimated fair value of stock options granted to employees and consultants during the three months ended July 31, 2021 and July 31, 2020, were calculated using the Black-Scholes option-pricing model using the following assumptions (Details)

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The estimated fair value of stock options granted to employees and consultants during the three months ended July 31, 2021 and July 31, 2020, were calculated using the Black-Scholes option-pricing model using the following assumptions (Details) - Employees And Consultants [Member]
3 Months Ended
Jul. 31, 2021
Jul. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Volatility 86.31%  
Dividend yield 0.00% 0.00%
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (in years) 2 years 6 months 2 years 6 months
Volatility   65.80%
Risk-free interest rate 1.01% 1.52%
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (in years) 5 years 6 years 3 months
Volatility   72.35%
Risk-free interest rate 1.07% 2.36%