Answer
(b) 5280 cars
(a) $4: 30 \mathrm{P.M}$
Work Step by Step
(a) The differentiation of the function gives $R^{\ prime}(t)=0.02t$, which contains a zero at $t=0$, and therefore the peak happens at 4:30 pm.
(b) The number of cars is an integral part of the $R(t)$ function.
$\int_{0}^{60} R(t) d t=\left.\left(-0.01 \frac{t^{3}}{3}+100 t\right)\right|_{0} ^{60}=5280$
