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

Time Series Value

$1$

$10\mathrm{.}12$

$2$

$10\mathrm{.}15$

$3$

$18\mathrm{.}58$

$4$

$23\mathrm{.}91$