Three particles P, Q and R, of masses 0.1 kg, 0.2 kg and 0.5 kg respectively, are at rest in a straight line on a smooth horizontal plane. Particle P is projected towards Q at a speed of 5 m/s. After P and Q collide, P rebounds with speed 1 m/s.

(a) Find the speed of Q immediately after the collision with P. [3]

Q now collides with R. Immediately after the collision with Q, R begins to move with speed V m/s.

(b) Given that there is no subsequent collision between P and Q, find the greatest possible value of V. [3]