Solving the Black-Scholes equation, we calculate the European call option price as c = SN(d1) KerT N(d2) where the K is the strike price and T is the time for the option to mature, and d =ln(S)+(r+2)T, 1K2 d2=d1 T (a) Prove that = N(d1). (b) Discuss the sign of and its significance. The suggested word limit for question 4 is 300 words.