235Black-Scholes formula where N(x) is cumulative standard normal distribution at x. In otherwords, it is the probability thata variable with a standard normaldistribution, i.e. N(0,1), will be less than x.Note: The equations for the call price and the put price are of course related via the put-call parity, i.e. viapt= c-Stt+ PV(E)t.()()() ()TddTTrS EddN
SdNEepd
NEed
N
ScttrTtrTttσσσ−=⎞ ⎟⎟ ⎠⎛ ⎜⎜ ⎝++
⎞ ⎟ ⎠⎛ ⎜ ⎝=−−−=−=−−122ln112212Derivative securities: Options - Black-Scholes modelBlack-Scholes model: Pricing formula