Answer
$39 \frac{m}{s}$
Work Step by Step
Integrating from $t = -2$ to $t = 6$, we have an area that is a right triangle with base $6$ and height $12$, so an area of $48$ and a smaller one to be subtracted with base $2$ and height $4$, so area $4$. Adding this to the initial speed of $7$, we have a final velocity of $39 \frac{m}{s}$
