A block kept on a frictionless horizontal surface is connected to one end of a horizontal spring of constant \( 100 \, \text{Nm}^{-1} \), 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 at a distance of \( 3 \) cm from the mean position is?