"In a large section of statistics class, the points for the final exams are normally distributed with a mean of 72 and a standard deviation of 9. Grades are to be assigned according to the following rule.

1) the top 10% receive A

2) the next 20% receive B

3) the middle 40%receive C

4) the next 20% receive D

5) the bottom 10% receive F.

Find the lowest score on the final exam that would qualify a student for an (A, B, C, D)