4. The sales (in millions of dollars) for an 18-month period are as follows. Month Sales 600 1 Month 9 10 2 775 600 3 11 Sales 600 775 600 575 625 650 600 4 650 12 13 5 6 14 700 800 550 775 7 15 8 a. Compare a three-month moving average forecast with an exponential smoothing forecast. Use a = 0.1. Which provides the better forecasts based on MSE? b. Find the forecast for the next month using the best forecast method. Page 2 of 3