Over a two$-$year period, the Topper Company sold the following numbers of lawn

mowers:

Month: $123456789101112$

Sales: $23822019524534538027022028012011085$

Month: $131415161718192021222324$

Sales: $135145185219240420520410380320290240$

a$.$ In column A input the numbers $1$ to $24$ representing the months and in

column B the observed monthly sales. Compute the three$-$month moving$-$average

forecast and place this in the third column. Be sure to align your forecast with the

period for which you are forecasting $($the average of sales for months $1,2,$ and $3$

should be placed in row $4$; the average of sales for months $2,3,$ and $4$ in row $5$; and

so on$.)$ In the fourth column, compute the forecast error for each month in which

you have obtained a forecast.