A major source of revenue in Texas is a state sales tax on
certain types of goods and services. Data are complied and the
state comptroller uses them to project future revenues for the
state budget. One particular category of foods is classified as
Retail Trade. Four years of quarterly data (in $ millions) for one
particular area of southeast Texas follow:

Using Excel find the following:

A) Compute seasonal indices for each quarter based on a CMA

B) Deseasonalize the data and develop a trend line on the
deseasonalized data

C) Use the trend line to forecast the sales for each quarter of
year 5

D) Use the season indices to adjust the forecasts found in part
C to obtain the final forecasts.