Using an initial estimate of $120,$ apply the exponential smoothing method retrospectively to last year's sales with $\backslash$alpha $=0\mathrm{.}1,0\mathrm{.}2,0\mathrm{.}3,0\mathrm{.}4,$ and $0\mathrm{.}5.$ Compare both MAD and MSE for these five values of the smoothing constant $\backslash$alpha $.$

MonthSalesJanuary $126$February$137$March$142$April$150$May$153$June$154$July$148$August$145$September$147$October$151$November$159$December$166$