Use regression analysis to fit a quadratic trend model to the data set.

a. What is the estimated regression function?
b. Compare the adjusted-R2 value for this model to that of the linear trend model. What is implied by this comparison?
c. Prepare a line graph comparing the quadratic trend predictions against the original data.
d. What are the forecasts for each of the next 6 months using this technique?
e. Calculate seasonal indices for each month using the results of the quadratic trend model.
f. Use these seasonal indices to compute seasonal forecasts for each of the next 6¢months.