The following data are the distances between a sample of 20 retail stores and a large distribution center that services them. The distances are in miles.

29; 37; 38; 40; 58; 67; 68; 69; 76; 86; 87; 95; 96; 96; 99; 106; 112; 127; 145; 150

Using the data set above, calculate:

a. sample mean

b sample variance

c standard deviation