Problem #42 Statistics Grade:

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

The top 10% receive A’s.

The next 20% receive B’s.

The middle 40% receive C’s.

The next 20% received D’s.

The bottom 10% receive F’s.

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