Thread: Proportions p=f/N

Suppose that the number of boxes of cookies sold by girl scouts in the state of Minnesota in 2012 follows a normal distribution with mean 45 and standard deviation 25.
What proportion of Minnesota girl scouts sold more than 50 boxes of cookies?

Now, I get that the formula for proportion is p=f/N but I do not know what to use for N!

Nevermind, I was supposed to use the Z score. Made the answer simple! Thanks anyways!