A piece of stone is released from rest from the rooftop of a building. It falls vertically under gravity It takes 6.6 s to reach the ground. Neglect air resistance. Take the acceleration due to gravity as 9.81 ms-2. If a bullet is fired vertically upwards with the speed calculated in (b), what is the maximum height that the bullet can reach?

I don't see any (a) or (b), but if the bullet's speed is the same as the rock's, it will rise as high as the rock started out.

and height H = (1/2) g t^2