PROBLEM $3($Causal Forecasting model$)$: $4$ POINTS $-$ SOLVE MANUALLY

NINJA$-$Ninja, Inc. wants to forecast its quarterly sales. Ninja$-$Ninja believes that its sales in a quarter are a

function of its total advertising ex penditures in the preceding two quarters combined. They have the

following data for the past two years:

$($a$)$ Construct a forecasting model that ex presses quarterly sales as a linear function of advertising

ex penditures in the previous two quarters com bined. $(3$ points$)$

$($b$)$ Use your forecasting model from part $($a$)$ to forecast sales in Quarter $1$ of Year $3.(1$ point$)$