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Note 17 - Stock-based Compensation Plans - Assumptions Used in Black-scholes Model for Each Grant (Details)
12 Months Ended
Jan. 31, 2021
Jan. 31, 2020
Jan. 31, 2019
Expected dividend yield (%)
Expected volatility (%) 26.40% 23.50% 23.60%
Risk-free rate (%) 0.70% 1.40% 2.00%
Expected option life (years) (Year) 5 years 5 years 5 years