Consider an option on a non-dividend-paying stock when the stock price is $60, the exercise price is $48, the risk-free interest rate is 5% per annum, the variance is 0.09 per year, and the time to maturity is 6 months. Use the Black-Scholes formula to calculate:

a. the price of the option if it is a European call

b. the price of the option if it is an American call

c. the price of the option if it is a European put

d. Verify that putcall parity holds