2.21 How much time do corporate executives exercise daily? Training programs exist to help executives improve their health so that they can think more clearly and make better business decisions. Suppose that we randomly sample ten executives and obtain the following daily exercise times (in minutes):

20 35 28 22 10 40 23 32 28 30

a. Find the mean daily exercise time.

b. Calculate the standard deviation using Equation 2.13.

c. Calculate the standard deviation using Equation 2.14.

d. Calculate the standard deviation using Equation 2.15.

e. Find the coefficient of variation.