A stone is allowed to fall from the top of tower 100 metre high and at the same time another stone is projected vertically upwards from the ground with a velocity of $25\;ms^{-1}$. The two stones will meets after

Question

$\begin{array}{1 1} 4\;s \\ 0.4\;s \\ 0.04\;s \\.40\;s \end{array}$