Using the data from the problem 10:

a. Using the average demand for the year as the base, compute a seasonal index for each month.

b. Use regression to estimate the deseasonalized demand in each of the given months. Using these base values, compute a seasonal index for each month.

c. Are the seasonal indices computed in parts a. and b. the same or different? Why?

d. Using the seasonal indices you computed in part b above also assumes a constant trend of +8 units per month and a forecast for December of 320 units. Compute a seasonally adjusted forecast for January, February, March, April, and May of the next year.