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Note 10 - Stock-based Compensation - Black-Scholes Option-pricing Model Assumptions (Details)
3 Months Ended
Nov. 30, 2019
Nov. 30, 2018
Dividend yield 2.15% 1.32%
Expected volatility 45.10% 45.80%
Expected life of option (years) (Year) 10 years 10 years
Average risk-free interest rate 1.57% 2.75%