(a) How high does the ball go?

How high does the ball go? At the top of its flight, the ball has an instantaneous velocity of zero. We plug v = 0 and yo = 0 into the equation:

v2 = vo2 + 2 a (y - yo)   to give:
y =
-vo2
2a
=
-144
-19.6
= 7.35 m

The ball goes 7.35 m high.