Suppose the dividends and interest incomes are taxed at the rate R but capital gains taxes are zero. Find the price formulas of the European put and call on an asset which pays a continuous dividend yield at the constant rate q, assuming that the riskless interest rate r is also constant. 

Explain why the riskless interest rate r and dividend yield q should be replaced by r(1 − R) and q(1 − R), respectively, in the Black–Scholes formulas.