A teacher gives a test to a large group of students. The results are closely approximated by a normal curve. The mean is 79 with a standard deviation of 4. The teacher wishes to give A's to the top 8% of the students and F's to the bottom 8%. A grade of B is given to the next 15%, with D's given similarly. All other students get C's. Find the bottom cutoff (rounded to the nearest whole number) for a B. (Hint: Use a table of areas under the standard normal curve to find z-scores from known A-values.) The bottom cutoff for a B is (Simplify your answer. Round to the nearest whole number as needed.) K