In a course where the mean final exam grade is 72 with a standard deviation of 6, the grading scheme is as follows:

The top 21% get As,

the next 23% get Bs,

the next 30% get Cs,

the next 10% get Ds, and

the rest get Fs.

Assume that the scores are normally distributed.

This question has 2 parts:

(a)What exam grade is the (minimum) cutoff for a B? Show enough work to make clear that you understand.

(b)What exam grade is the (minimum) cutoff for a D? Show enough work to make clear that you understand.