In the figure shown, `m_(a)=m_(b)=1kg` block-`A` is neutral while block-`B` carries charge `-1c`. Sizes of `A` and `B` are negligible. Block-`B` is released from rest at a distance `1.8m` from `A`. Initially spring is neither compressed nor stretched.
If collision between `A` and `B` is perfectly inelastic, then velocity of the combined mass just after collision is
A. `6m//s`
B. `3m//s`
C. `9m//s`
D. `12m//s`
