Refer to Problem 21. Suppose that the following are the quarterly sales data for the past seven years:

a. Show the four-quarter moving average values for this time series. Plot both the original time series and the moving averages on the same graph.
b. Compute the seasonal indexes for the four quarters.
c. When does Hudson Marine experience the largest seasonal effect? Does this result seem reasonable?Explain.

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Year Quarter Quarter 2 Quarter 3 Quarter Total Sales 15 18 26 28 34 36 10 15 23 4 10 14 19 20 24 28 12 18 21 20 27 35 50 75 90 105 110 130 28 30 35