Capacitor collision

Two fixed very large conducting plates $A$ and $B$ of area $S$ carry charges $-Q$ and $q$ respectively, where $Q > q > 0$ . A third identical plate $C$ carrying a charge $Q$ is released at distance $d$ from $B$ . Third plate collides with $B$ . Assume collision is elastic and time of collision is sufficient to redistribute charge among $B$ and $C$ (neglect gravity):

A: Force acting on plate $C$ before collision is $\dfrac {(Q-q)Q}{2\epsilon_0 S}$ .

B: Force acting on plate $C$ after collision is $\dfrac {(q/2)^2}{2\epsilon_0 S}$ .

C: Subsequent to collision kinetic energy of plate $C$ increases.

D: Subsequent to collision electrostatic potential energy between the plates remains constant.