In a Statisctics course the professor uses the following grading policy: the bottom 5% of students receive an F, the next 10% receive a D, the next 40% receive a C, the next 30% receive a B, and the rest receive an A. Assume Students grades are Normally distributed with a mean of 70 and standard deviation of 10. Give the cut off scores for each letter grade: a. A/B
b. B/C
c. C/D
d. D/F