Hi, not been online in some time but back again now with some more probably simple questions

I can't get my head around this question involving collisions, it's a bit wordy to please bear with me.

Obviously the final velocity of B needs to be greater than 2, but I'm having trouble making this into an equation?3 smooth identical spheres each of mas 1kg move on a straight line on a smooth horizontal floor. B lies between A and C.

Spheres A and B are projected towards each other with speeds 3 m/s and 2 m/s respectivly, and C is projected away from sphere A at a speed of 2m/s.

The coefficient of restitution between any two spheres ise, show that sphere B will only collide with C ife> $\displaystyle \frac{3}{5}$

Thanks in advance

Craig