20) A history teacher assigns letter grades on a test according to the following scheme:
A: Top 10%
B: Scores below the top 10% and above the bottom 60%
C: Scores below the top 40% and above the bottom 20%
D: Scores below the top 80% and above the bottom 10%
F: Bottom 10%
Scores on the test are normally distributed with a mean of 68 and a standard deviation of 12.1. Find the numerical limits for each letter grade. 20) ______
A) A: Above 83
B: Between 71 and 83
C: Between 58 and 70
D: Between 53 and 57
F: Below 53
B) A: Above 79
B: Between 71 and 79
C: Between 58 and 70
D: Between 53 and 57
F: Below 53
C) A: Above 79
B: Between 71 and 79
C: Between 58 and 70
D: Between 55 and 57
F: Below 55
D) A: Above 83
B: Between 74 and 83
C: Between 58 and 73
D: Between 53 and 57
F: Below 53