This is the problem:

A Ball is thrown into the air with an initial velocity of 64 feet per second. the height of the ball(in feet) [I]t[I] seconds after it is shot into the air is given by the function h(t)=-16t^2+64t

a)How many seconds after the ball is thrown does it reach its maximum height and what is this height?

b) How many seconds after the ball is thrown does it hit the ground?

I do not have a clue how to solve this