Where Call = the value of a call option on a share of non-dividend-paying stock
P = the current share price
K = the exercise price of the call option
I = a constant risk-free rate of interest in continuously compounded returns
ơ = the instantaneous standard deviation of return on the stock
T = the time to expiration of the option expressed as a fraction of one period
D1 = [ln(P/K) + (I + (ơ2/2))T] / (ơ√T)
D2= (d1 - ơ√T)
N(.)=the standard normal cumulative distribution function
The value of a put option on a share of stock can be found from put-call parity, which is stated in continuously compounded returns as
Call-Put = P - e(-iT)K Put = Call - P +e(-iT)K(6A.2)