Week Sales (1000s of gallons) 1 17 2 21 3 19 4 23 5 18 6 16 7 20 8 18 9 22 10 20 11 15 12 22 a. Compute four-week and five-week moving averages for the time series (to 2 decimals). Time Series 4-Week Moving 5-Week Moving Week Value Average Forecast (Error)2 Average Forecast (Error)2 Totals b. Compute the MSE for the four-week and five-week moving average forecasts (to 2 decimals). MSE (-Week) MSE (-Week) c. What appears to be the best number of weeks of past data (three, four, or five) to use in the moving average computation