Hi,

could you help me to solve this problem?

9. A college professor teaches Econ 120A each fall to a large class of students. For tests, he uses the stan- dardized exams that he knows from past experience produce bell-shaped distributions with a mean of 70 and a standard deviation of 12. His philosophy of grading is to impose standards that will yield, in the long run, 14% A's, 20% B's, 32% C's, 20% D's and 14% F's. Where should the cutoff be between the A's and the B's? Between the B's and the C's