Consider the sales data for Computer Success given in Problem $7.$

a$.$ Use a $3-$month weighted moving average to forecast the sales for the months April through December. Use weights of $(4/8),(3/8),$ and $(1/8),$ giving more weight to more recent data.

b$.$ Use exponential smoothing with $=0\mathrm{.}6$ to forecast the sales for the months April through December. Assume that the initial forecast for January was $$3,200.$ Start error measurement in April.

c$.$ Compare the performance of the two methods by using the mean absolute deviation as the performante criterion, with error measurement beginning in April. Which method would you recommend?

d$.$ Compare the performance of the two methods by using the mean absolute percent error as the performance criterion, with error measurement beginning in April. Which method would you recommend?

e$.$ Compare the performance of the two methods by using the mean squared error as the performance criterion, with error measurement beginning in April. Which method would you recommend?