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本帖最後由 hkcarnby 於 10-2-7 07:55 PM 編輯
Black–Scholes formula
The Black Scholes formula is used for obtaining the price of European put and call options. It is obtained by solving the Black–Scholes PDE - see derivation below.
Using this formula, the value of a call option in terms of the Black–Scholes parameters is:
C(S,t) = SN(d_1) - Ke^{-r(T - t)}N(d_2) \,
d_1 = \frac{\ln(\frac{S}{K}) + (r + \frac{\sigma^2}{2})(T - t)}{\sigma\sqrt{T - t}}
d_2 = d_1 - \sigma\sqrt{T - t}.
The price of a put option is:
P(S,t) = Ke^{-r(T-t)}N(-d_2) - SN(-d_1). \
For both, as above:
* N(•) is the cumulative distribution function of the standard normal distribution
* T - t is the time to maturity
* S is the spot price of the underlying asset
* K is the strike price
* r is the risk free rate (annual rate, expressed in terms of continuous compounding)
* σ is the volatility in the log-returns of the underlying
http://en.wikipedia.org/wiki/Black%E2%80%93Scholes |
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