For the demand data below, use time series decomposition to make a forecast for the four quarters of

$2023.$ Use the multiplicative model. You should use the Least Squares Regression discussed in class. Write

clearly everysteps of your forecasting, as partial points will be given. $(5$pts$)(1$pt for seasonal factor, $1$pt for

deseasonalized demand, $2$ pts for linear regression output, $1$pt for final forecast$)$

Year Season t

Demand

$($in $1000)$

$2021$ Spring $1205$

Summer $2140$

Fall $3375$

Winter $4575$

$2022$ Spring $5475$

Summer $6275$

Fall $7685$

Winter $8965$