At an amusement park, there are $200-\mathrm{kg}$ bumper cars $A, B,$ and $C$ that have riders with masses of $40 \mathrm{~kg}, 60 \mathrm{~kg}$, and $35 \mathrm{~kg}$, respectively. Car $A$ is moving to the right with a velocity $\mathbf{v}_{A}=2 \mathrm{~m} / \mathrm{s}$ and $\operatorname{car} C$ has a velocity $v_{B}=1.5 \mathrm{~m} / \mathrm{s}$ to the left, but car $B$ is initially at rest. The coefficient of restitution between each car is $0.8 .$ Determine the final velocity of each car, after all impacts, assuming ( $a$ ) cars $A$ and $C$ hit car $B$ at the same time, $(b)$ car $A$ hits car $B$ before car $C$ does.