A block of mass $m=0.1\;kg$ is connected to a spring of unknown spring constant k. It is compressed to a distance x from its equilibrium position and released from rest. After approaching half the distance $\bigg(\large\frac{x}{2} \bigg)$ from equilibrium position, it hits another block and comes to rest momentarily, while the other block moves with a velocity $3 ms^{-1}$. The total initial energy of the spring is :

Question

$\begin{array}{1 1} 1.5\;J \\ 0.6\;J \\ 0.3\;J \\ 0.8 \;J \end{array}$