A cosmetics manufacturer's marketing department has developed a linear trend equation that can be used to predict annual sales of its popular Hand & Fo$8$ ot Cream.

$F_t=80+15t$

where

$F_t=$ Annual Sales $(000$ bottles$)$

$t=0$ corresponds to $1990$

a$.$ Are annual sales increasing or decreasing? By how much?

Annual sales are

ly

thousands bottles per year