(a) How high does it go?

At the very top of its flight, the ball has an instantaneous velocity of zero. We can plug v = 0 into the equation:

v² = v_o² + 2 a (x - x_o)

This gives:

0 = 144 + 2 (-9.8) x

Solving for x gives x = 7.35 m, so the ball goes 7.35 m high.