6 A particle \(A\) of mass \(2 m\) is moving with speed \(u\) on a smooth horizontal surface when it collides with a stationary particle \(B\) of mass \(m\). After the collision the speed of \(A\) is \(v\), the speed of \(B\) is \(3 v\) and the particles move in the same direction.

1. Find \(v\) in terms of \(u\).
2. Show that the coefficient of restitution between \(A\) and \(B\) is \(\frac { 4 } { 5 }\).
   \(B\) subsequently hits a vertical wall which is perpendicular to the direction of motion. As a result of the impact, \(B\) loses \(\frac { 3 } { 4 }\) of its kinetic energy.
3. Show that the speed of \(B\) after hitting the wall is \(\frac { 3 } { 5 } u\).
4. \(B\) then hits \(A\). Calculate the speeds of \(A\) and \(B\), in terms of \(u\), after this collision and state their directions of motion.