One end of a spring of force constant $k$ is fixed to a vertical wall and the other to a block of mass $m$ resting on a smooth horizontal surface. There is another wall at a distance $x_{0}$ from the block. The spring is then compressed by $2 x_{0}$ and then released. The time taken to strike the wall iv
(a) $\frac{1}{6} \pi \sqrt{\frac{k}{m}}$
(b) $\sqrt{\frac{k}{m}}$
(c) $\frac{2 \pi}{3} \sqrt{\frac{m}{k}}$
(d) $\frac{\pi}{4} \sqrt{\frac{k}{m}}$