A company has collected the following quarterly demand data for one if its products. Use the information provided to develop a forecast for periods 13 through 16 using classical decomposition of a time series.
Period a t
1…………………………..1178
2…………………………..1239
3…………………………..1311
4…………………………..1067
5…………………………..1361
6…………………………..1467
7…………………………..1623
8…………………………..1291
9…………………………..1631
10…………………………..1700
11…………………………..1772
12…………………………..1443