Two particles start moving towards each other will constant acceleration of $ 1\;m/s^2$ . If their initial separation is 100 m, find after what time they will meet each other

Question

$\begin{array}{1 1} (a)\;5\;s \\ (b)\;10\;s \\ (c)\;15\;s \\ (d)\;20\;s \end{array} $