Probability — practice question

A particle $P$ with mass $0.1\,\text{kg}$ is fixed to one end of a light elastic string whose natural length is $0.4\,\text{m}$ and modulus of elasticity is $12\,\text{N}$. The opposite end of the string is fastened to a fixed point $O$ on a smooth horizontal plane. $P$ travels across the surface in a horizontal circle with centre $O$ and radius $0.6\,\text{m}$.