Problem 3-20 In this problem, you are to test the validity of your forecasting model. Here are the forecasts for a model you have been using and the actual demands the WEEK FORECAST ACTUAL 1 790 825 2 775 925 3 875 975 4 875 825 5 925 825 6 900 1,070 a. Use the method stated in the text to compute the MAD and tracking signal for each week. (Negative values should be indicated by a minus sign. place and all other answers to the nearest whole number.) Absolute Deviation Sum of Absolute Deviation Deviation RSFE MAD TS Week Forecast Actual 1 790 825 2 775 925 3 875 975 4 875 825 5 925 825 6 900 1,070 b. Decide whether the forecasting model you have been using is giving reasonable results The forecasting model is acceptable M