Quarterly data for the most recent three years of a products demand is shown below. Use the

Question:

Quarterly data for the most recent three years of a product’s demand is shown below. Use the data to develop a forecast for periods 13 through 16 using classical decomposition of a time series.
Period a a
1………………………….575
2………………………….590
3………………………….610
4………………………….485
5………………………….605
6………………………….638
7………………………….691
8………………………….538
9………………………….666
10………………………….680
11………………………….695
12………………………….555