Newton's laws of motion — practice question

The diagram shows a particle $A$ of mass $1.6\,\text{kg}$ on a horizontal plane, and a particle $B$ of mass $2.4\,\text{kg}$ on a plane inclined at an angle of $30^\circ$ to the horizontal. The particles are joined by a light inextensible string that goes over a small smooth pulley $P$ fixed at the top of the inclined plane. The distance $AP$ is $2.5\,\text{m}$ and the distance of $B$ from the bottom of the inclined plane is $1\,\text{m}$. A barrier at the bottom of the inclined plane stops any further movement of $B$. The section $BP$ of the string is parallel to a line of greatest slope of the inclined plane. The particles are released from rest, with both sections of the string taut.