The following table shows the past two years of quarterly sales information. Assume that there are both trend and seasonal factors and that the seasonal cycle is one year. Use time series decomposition to forecast quarterly sales for the next year.

Quarter ........ Sales

1 ........ 160

2 ........ 195

3 ........ 150

4 ........ 140

5 ........ 215

6 ........ 240

7 ........ 205

8 ........ 190