Two balls `A` and `B` of masses 0.3 kg and 0.2 kg respectively are moving along positive X-axis and negaive X-axis with velocities 2.0 m `//` s. They collide and thereafter move in the directions opposite to their original directions. Find the velocities of `A` and `B` after collision. Also, calculate total K.E. of the ball before and after collision.