Probability — practice question

A particle $P$ with mass $0.3\,\text{kg}$ is fastened to one end of a light elastic string whose natural length is $0.6\,\text{m}$ and modulus of elasticity is $9\,\text{N}$. The other end of the string is fixed at a point $O$ on a smooth plane inclined at $30^\circ$ to the horizontal. $OA$ is the line of greatest slope of the plane, with $A$ below the level of $O$ and $OA = 0.8\,\text{m}$. The particle $P$ is released from rest at $A$.