An overhead view of part of a pinball game is shown. If the plunger imparts a speed of $3 \mathrm{m} / \mathrm{s}$ to the ball which travels in the smooth horizontal slot, determine the acceleration a of the ball
(a) just before it exits the curve at $C$ and $(b)$ when it is halfway between points $D$ and
$E .$ Use the values $r=150 \mathrm{mm}$ and $\theta=60^{\circ}$