For the given quarterly sales data, a) calculate seasonal indices for each quarter, b) the year 4 annual forecast based on a linear regression trend forecasting method, c) the seasonally adjusted trend based quarterly forecasts for that 4th year, d) the year 4 annual forecast based on the Naive forecasting method, and e) the seasonally adjusted Naive based quarterly forecast for that 4th year.

Quarter:	Year 1	Year 2	Year 3
1	2	3	7
2	6	10	18
3	2	6	8
4	5	9	15
Total	15	28	48

a) Seasonal indices: Q1 ; Q2 ; Q3 ; Q4

b) Year 4 forecast, trend based: Year 4

c) Seasonally adjusted trend forecast, year 4: Year 4 Q1 ; Year 4 Q2 ; Year 4 Q3 ; Year 4 Q5

d) Year 4 forecast, Naive based: Year 4

e) Seasonally adjusted Naive forecast, year 4: Year 4 Q1 ; Year 4 Q2 ; Year 4 Q3 ; Year 4 Q5