A particle $A$ of mass 3 kg and a particle $B$ of mass 6 kg are connected by a light inextensible string. The string passes over a smooth pulley fixed at the top of a rough inclined plane. The coefficient of friction between the particle $A$ and the plane is 0.25. The plane is inclined at an angle of ${\alpha }^{\circ }$ to the horizontal such that $\cos \alpha =0.6$. $A$ lies on the plane and $B$ hangs freely from the edge of the plane 1.5 m above the ground with the string taut. The system is released from rest. Assume $B$ hits the ground before $A$ reaches the pulley.