Solve using excel. Knowing that, for a medium$-$sized dealership, the vehicle sales forecast for week $4$ was $85$ units: a$)$ Use the exponential smoothing with an alpha of $0\mathrm{.}45$ to forecast sales for periods $5$ through $10.$ b$)$ Estimate the tracking signal for your forecasts. Would you recommend this forecasting model? $\backslash$begin$\{$tabular$\}\{|$c$|$c$|\}\backslash$hline Week & Sales $($units$)\backslash \backslash \backslash$hline $1$ & $100\backslash \backslash \backslash$hline $2$ & $120\backslash \backslash \backslash$hline $3$ & $112\backslash \backslash \backslash$hline $4$ & $90\backslash \backslash \backslash$hline $5$ & $115\backslash \backslash \backslash$hline $6$ & $113\backslash \backslash \backslash$hline $7$ & $108\backslash \backslash \backslash$hline $8$ & $100\backslash \backslash \backslash$hline $9$ & $110\backslash \backslash \backslash$hline $10$ & $99\backslash \backslash \backslash$hline $11$ & $125\backslash \backslash \backslash$hline $\backslash$end$\{$tabular$\}$