2.28 An online pharmaceutical company obtained the following frequency distribution of shipping times

(number of hours between the time an order is placed and the time the order is shipped) for a random sample of 40 orders. (Be sure to complete all appropriate columns and show your work).

Number of Hours fi 4 6 10 8 10 6 16 15 16 6 22 10 22 6 28 7

a. What is the approximate mean shipping time?

b. What is the approximate variance and standard deviation?