Answer
$a.$
$D(v)=0.05v^{2}+2.6v-15$
$b$.
$D(60)=321$
$c$.
At 60 mph, upon observing the impediment,
the car will need 321 feet to stop.
Work Step by Step
$a.$
$D(v)=R(v)+B(v)$
$D(v)=2.2v+0.05v^{2}+0.4v-15$
$D(v)=0.05v^{2}+2.6v-15$
$b$.
$D(60)=0.05(60)^{2}+2.6(60)-15$
$=180+156-15$
$=321 $ (ft)
$c$.
At 60 mph, upon observing the impediment,
the car will need 321 feet to stop.
