What If a set of grades on a statistics examination are approximately normally distributed with the mean of 74 and a standard deviation of 7.9? When:

a. The lowest passing grade is the lowest 10% of the student are given F’s;
b. The highest B is the top 5% of the students are given A’s.
c. The lowest B if the top 10% of the students are given A’s and the next 25% of the students are
given B’s.