Demand for the past 8 weeks are 130, 108, 149, 121, 146, 123, 132, 143. Use the following methods to forecast demand in the next week: (1) 3-week simple moving average; (2) 3-week weighted moving average, with weights 0.1, 0.3, 0.6 for week t-3, t-2, t-1; (3) simple exponential smoothing with alpha=0.2.

For each method, compare the forecast and demand in Week 4-8 and calculate forecasting errors, MAD, MSE, and MAPE.

Week	Demand
1	130
2	108
3	149
4	121
5	146
6	123
7	132
8	143