A car starts from rest , moves with an acceleration $a$ and then decelerates at $b$ for some time to come to rest. If the total time taken is t, the maximum velocity is

Question

$\begin{array}{1 1} \large\frac{abt}{a+b} \\ \large\frac{a^2t}{a+b} \\ \large\frac{at}{a+b} \\\large\frac{b^2t}{a+b} \end{array} $