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BENEFIT PLANS - Assumptions used in determining net periodic pension cost (Details)
12 Months Ended
Apr. 30, 2021
Apr. 30, 2020
BENEFIT PLANS    
Discount rate used to determine net periodic pension cost 2.29% 3.54%
Discount rate used to determine pension benefit obligation 2.48% 2.29%
Expected long-term rate of return on assets used for pension cost on assets 7.75% 7.75%