Work Energy And Power

A block kept on a frictionless horizontal surface is connected to one end of a horizontal spring of constant $100 \mathrm{Nm}^{-1}$ whose other end is fixed to a rigid vertical wall. Initially the block is at its equilibrium position. The block is pulled to a distance of 8 cm and released.The kinetic energy of the block when it is a distance of 3 cm from the mean position is