Given the following graph, where the y-axis is velocity (m/s) and the x-axis is space (m):
$v(s) = \begin{cases} \sqrt{5s} & s < 20 \\ 10 & s \geq 20 \end{cases}$
The question is about how much time the body needs to move the first 100 meters.
From 20 to 100 meters it needs 8 seconds. But I'm not sure how to solve the square root part. How can it be solved by integration?