$(12$ points$)$ The following equation summarizes the trend projection of quarterly sales of condos over a long cycle. Sales exhibit seasonal variation. Using the information given, prepare seasoned forecast of sales for each quarter of next year $($not this year$).$

$F_t=40-6\mathrm{.}5t+2t^2,$ where $F_t=$ Unit sales, $t=1$ is $1^{st}$ quarter of last year

Assume seasonal relatives $Q1=1\mathrm{.}1,Q2=1\mathrm{.}0,$ and $Q3=0\mathrm{.}6$

Find Q$4$ seasonal relative: Seasonal relatives adds to the number of seasons;