need help plz

The perpendicular bisector of the line segment connecting the points (-3,8) and (-5,4) has an equation of the form y=mx+b. Find m+b.

Note: The perpendicular bisector of the line segment $\overline{AB}$ is the line that passes through the midpoint of $\overline{AB}$ and is perpendicular to $\overline{AB}$.