From Exercise $9$ of Chapter $7$of the textbook: $(35$ points$)$

Quarterly demand for smartphone at a retailer is as shown. After obtaining initial estimates for level, trend, and seasonal factors, forecast quarterly demand for year $5$ using Winter$$s model with $\backslash$alpha $=0\mathrm{.}05,\backslash$beta $=0\mathrm{.}1,$ and $\backslash$gamma $=0\mathrm{.}15.$ Evaluate the MAD, MAPE, and MSE. Please feel free to use the Excel file provided to you as part of this assignment. Please plot the demand data and your demand forecasts.

Year Quarter Demand

$1$ I $513$

II $932$

III $1,509$

IV $1,902$

$2$ I $693$

II $1,163$

III $1,857$

IV $2,469$

$3$ I $846$

II $1,439$

III $2,271$

IV $3,079$

$4$ I $1,070$

II $1,751$

III $2,785$

IV $3,613$