On Wiki there is the following example:
![newspaper-problem.PNG newspaper-problem.PNG](https://community.jmp.com/t5/image/serverpage/image-id/29718i0AABF010B6947948/image-size/large?v=v2&px=999)
This is the associated JSL code:
mu = 50;
sd = 20;
retailPrice = 7;
purchasePrice = 5;
quantity = normal quantile( (retailPrice-purchasePrice)/retailPrice, mu, sd);
This is the calculation for optimal quantity, not probability which is what you asked for, but maybe points you in the right direction.
-Dave