Can you show how to do it in Excel with the formulas?

7. Refer to the gasoline sales time series data in Table 15.1. a. Compute four-week and five-week moving averages for the time series. b. Compute the MSE for the four-week and five-week moving average forecasts. What appears to be the best number of weeks of past data (three, four, or five) to use in the moving average computation? Recall that MSE for the three-week moving average is 10.22. c. TABLE 15.1 GASOLINE SALES TIME SERIES Week 1 2 3 4 5 Sales (1000s of gallons) 17 21 19 23 18 16 20 18 22 20 15 22 7 8 9 10 11 12