User blog comment:Tuner King 5/Help plz/@comment-24808864-20160112230745/@comment-24808864-20160112231711

Before pointing out an error in your derivative calculation, it is important to notice that even if we do get an answer to this problem, it won't make "sense" in the problem because the variable n is discrete. Since it represents a number of people, and you can't have a fraction or a decimal of a person, the variable is not continuous and therefore traditional continuous calculus methods should not be employed. You are looking for something called discrete math technically, in which case you would literally calculate P(2)-P(1) and P(3)-P(2) and so forth until you found the one which was the largest change.