A ball is thrown horizontally with speed v from the floor at the top of some stairs as shown in the figure given below. The width and height of each step are both equal to \( l \) . What should v be so that the ball barely clears the corner of the step that is 4 steps down? Assume \( l = 25 \text{ cm} \) and \( g = 10 \text{ ms}^{-2} \) .

A \( 2\sqrt{5} \)

B \( \sqrt{5} \)