Consider the given dataset:

$\backslash$table$[[$Year$,$Quarter,Demand,Year,Quarter,Demand$],[1,1,513,3,1,846],[,2,932,,2,1439],[,3,1509,,3,2271],[,4,1902,4,4,3079],[2,1,693,4,1,1070],[,2,1163,185,2,1751],[,3,2469,,3,2785],[,4,,4,3613,]]$

a$.$ After obtaining initial estimates for level, trend and seasonal factors, forecast demand for year $5$ using Winter's model with $=0\mathrm{.}05,=0\mathrm{.}10$ and $=0\mathrm{.}15$

b$.$ Compute MAD, MSE and MAPE, bias and Tracking Signal for the forecast.

c$.$ Can you find values of $,,$ and $$ that result in a lower MAD? How? Show your calculations.

NOTE: You should use MS Excel in order to answer these questions. Submit your excel working file!