A spherical ball of mass 20kg is stationary at the top of a hill of height 100m.It rolls down a smooth surface to the ground and then climbs up another hill of height 30m and finally rolls down to a horizontal base at a height of 20m above the ground.The velocity attained by the ball is

Question

$\begin{array}{1 1}40ms^{-1}\\20ms^{-1}\\10ms^{-1}\\10\sqrt{30}ms^{-1}\end{array}$