Answer
Maximum rise: $19.5$ feet
Work Step by Step
We know that the definition of slope is:
$slope=\frac{rise}{run}$
In this case, we have the maximum slope of 13% (slope=0.13) and a run of 150 ft. We calculate the maximum rise:
$slope=\frac{rise}{150}=0.13$
$rise=0.13*150$
$rise=19.5$ feet