Exponential smoothing forecast

Smoothing constant:

$0\mathrm{.}8$

$($iii$)$ Enter appropriate formulae in the shaded cells to calculate an exponential smoothing forecast for week $9$ demand.

You should use the smoothing constant specified above and week one demand as the starting forecast for week two.

$($iv$)$ Use the forecasts from weeks $4$ to $8$ to calculate the MAPE.