A ball is projected upward from the top of a 90-foot building at a velocity of 64 feet per second. The ball's height above the ground below the building is described by the function h(t) = -16t^2 + 64t + 90, with t being the time in seconds after the ball is projected upward.
c. Write the coordinates of the vertex. Interpret what these numbers mean in the context of the problem.
d. If nothing stops the ball before, then how much time elapses until the ball hits the ground below the building?