A ball at rest is dropped freely from a height of 20 m. It loses 30% of its energy on striking the ground and bounces back. The height to which it bounces back is

Question

$\begin {array} {1 1} (1)\;14\: m & \quad (2)\;12\: m \\ (3)\;9\: m & \quad (4)\;6\: m \end {array}$