$($a$)$ Compute four$-$week and five$-$week moving averages for the time series.

$\backslash$table$[[$Week$,\backslash$table$[[$Time Series$],[$Value$]],\backslash$table$[[4-$Week$],[$Moving$],[$Average$],[$Forecast$]],\backslash$table$[[5-$Week$],[$Moving$],[$Average$],[$Forecast$]]],[1,17,,],[2,21,,],[3,19,,],[4,23,,],[5,18,,],[6,16,,],[7,20,,],[8,18,,],[9,22,,],[10,20,,],[11,15,,],[12,22,,]]$

$($b$)$ Compute the MSE for the four$-$week moving average forecasts. $($Round your answer to two decimal places.$)$

Compute the MSE for the five$-$week moving average forecasts. $($Round your answer to two decimal places.$)$

Three weeks appears to be best, because the three$-$week moving average provides the smallest MSE.

Three weeks appears to be best, because the three$-$week moving average provides the largest MSE.

Four weeks appears to be best, because the four$-$week moving average provides the smallest MSE.

Five weeks appears to be best, because the five$-$week moving average provides the smallest MSE.