Here are two strategies, which have the same maturity (1 year), and based on the same stock (no dividend).

Strategy1: Long a call(C1) with X1=$37 and Long a put(P1) with X2=$56;

Strategy2: Long a put (P2) with X1=$37 and Long a call(C2) with X2=$56;

a. If they have the same costs, which strategy would investors choose? (please explain with payoff diagram).

b. If current stock price is $50, and risk-free rate is 0.7% p. a. The price of both C1 and P1 give the same volatility of 34% p. a. for the stock. What is the cost of Strategy1 by using Black-Scholes model?