Apply a moving average with window span of w $=4$ to the data. Consider the department store sale excel file.

Use all but the last year $(2023)$ as the training set.

a$.$ Create a time plot of the moving average series.

b$.$ Use the MA$(4)$ model to forecast appliance sales in Q$1-2024$ and Q$1-2025.$ What does MA$(4)$ chart reveal?

c$.$ Apply Holt$-$Winter$$s exponential smoothing with an appropriate season length $($you should decide$)$ and smoothing parameters of $\backslash$alpha $=0\mathrm{.}2\backslash$beta $=0\mathrm{.}15\backslash$gamma $=0\mathrm{.}05.$