A car acceleration from rest at a constant rate $\alpha$ for some time after which it decelerates at a constant rate $\beta$ to come to rest. If t is the total time elapsed , then the maximum velocity attained by the car is

Question

$\begin{array}{1 1} \alpha \beta t \\ \large\frac{t}{\alpha \beta } \\ \large\frac{\alpha \beta t}{\alpha+ beta} \\\large\frac{\alpha+ \beta t}{\alpha \beta}\end{array} $