A textbook publisher has compiled data on the total annual sales of its business textbooks for the past nine years:

Year 1 2 3 4 5 6 7 8 9 Sales (x 1000) 39 44 48 52 55 57 62 69 73

a) Using the appropriate model, predict textbook sales for the next five years.

b) Prepare a control chart for the forecast using the original data and limits of 3 types of deviation.

c) Assume that actual sales for the next five years will be:

Year 10 11 12 13 14 Sales (x 1000) 77 82 87 91 50

What do you think about the effectiveness of the prediction method?