On a recent analytics exam, the scores were normally distributed, with a mean of 76 and a standard deviation of 10.Letter grades for the exam were based on a classic scale, with 90-100 = A; 80-89 = B; 70-79 = C; 60-69 = D; below 69 = F.

1) What percentage of the class would you expect to have earned an A?

a) about 8%

b) less than 1%

c) about 5%

d) about 42%

2) What percentage of the class would you expect to have earned a B?

a) about 40%

b) about 25%

c) about 55%

d) about 15%

3) If you formed a sample from the four people on the front row, what is the probability that the mean of their scores was greater than 80?

a) about 29%

b) about 55%

c) about 25%

d) about 21%