When the non-dividend paying stock price is $20, the strike price is $20, the risk-free rate is 5%, the volatility is 20% and the time to maturity is 3 months which of the following is the price of a European put option on the stock
a. 19.7N(-0.1)-20N(-0.2)
b. 20N(-0.1)-20N(-0.2)
c. 19.7N(-0.2)-20N(-0.1)
d. 20N(-0.2)-20N(-0.1)