I have this model
So=75 K=80 r=0,02 sigma=0,25 T=1
which gives me: ln(75/80)+(0,002-(1/2*o,25^{2})*1/o,25*1 = -0,3032
Since its probability it can't be negative...??
Is part of that equation $\displaystyle (r-\frac{1}{2}\cdot \sigma^2)$ or $\displaystyle (r-\frac{1}{2\sigma^2})$ or $\displaystyle (r-\frac{1}{2})\cdot \sigma^2$ or $\displaystyle \frac{r-1}{2\sigma^2}$