COMPLETE ALL INTERVALS A THROUGH D$!!!$

The position of an object moving along a line is given by the function $s(t)=-19t^2+152t.$ Find the average velocity of the object over the following intervals.

$($a$)1,5$

$($b$)1,4$

$($c$)1,3$

$($d$)1,1+h$ where $h>0$ is any real number.

$($a$)$ The average velocity of the object over the interval $1,5$ is $38.$

$($b$)$ The average velocity of the object over the interval $1,4$ is $$