You have collected data on a firms sales (in units) for a product line during the past 16 weeks. Using the following forecasting technique, determine the forecast for period 17, 18, 19, and 20?: Additive seasonality (assume 5th month demand to be 240 units

Weeks Sales (units) 25 1 2 35 3 45 65 4 5 28 6 38 7 44 8 69 9 31 41 10 11 48 12 13 14 74 35 45 15 52 16 78