please don't solve with excel. I need hand writing solution

2. The following demand data was collected over a three-year period for one product. a. Use the data to develop a regression-based forecasting considering seasonal impacts. b. Use the data to develop a three-period weighted moving averages method. c. Compare a and b using MAD values. | d. Give the best forecast for the l* month of 4th year using the best method of a or b. Month 1 2 3 4 5 6 7 8 9 10 5 Demand, year 1 72 67 85 99 87 135 127 131 102 96 88 79 Demand, year 2 84 98 86 113 121 140 133 156 125 134 118 102 Demand, year 3 97 119 138 124 143 162 157 178 136 141 122 120 11 12