Using the data below, what is the weighted moving average forecast for the $4$th week? The weights are $\mathrm{.}20,\mathrm{.}30,\mathrm{.}50($oldest period to most recent period$)$ Week $12$ Time Series Value $18\mathrm{.}0020\mathrm{.}00316\mathrm{.}0012\mathrm{.}00$