You are given the following partial demand and forecast data for a product:

$\backslash$table$[[$Quarter $($t$)$:$,4,5,6],[$Forecast $($Ft$)$:$,400,430,600],[$Demand $($Dt$)$:$,420,370,680]]$

Compute a $3-$quarter simple moving average forecast for quarter $7.$

A$.F7=476\mathrm{.}67$

B$.F7=490$

C$.F7=680$

D$.F7=600$