The quarterly sales data (number of copies sold) for a college textbook over the past 3 years are as follows in the Table below:

(a)Compute seasonal indexes for the 4 quarters.

(b) When does the textbook publisher experience the largest change in sales? Does this result appear to be reasonable? Explain.

(c) Using the information on seasonality, compare a 4-quarter moving average to trend projection model and an exponential smoothing with a smoothing constant of 0.2.

Quarter 1 2 3 4 QUARTERLY SALES Year 1 16 9 26 25 Year 2 18 9 29 23 Year 3 18 11 29 26