Newton's laws of motion — practice question

Particles $A$ and $B$, with masses $m\,\text{kg}$ and $0.3\,\text{kg}$ respectively, are fastened to the two ends of a light inextensible string. The string goes over a fixed smooth pulley, and the particles hang freely beneath it. The system is let go from rest, with both particles $0.8\,\text{m}$ above horizontal ground. Particle $A$ reaches the ground at a speed of $0.6\,\text{m s}^{-1}$.