A ball is thrown vertically upward from the top of a building 64 feet

A ball is thrown vertically upward from the top of a building 64 feet tall with an initial velocity of 48 feet per second. The distance s (in feet) of the ball from the ground after t seconds is s = 64+48t-16t^2.
A.) After how many seconds does the ball strike the ground.
B.) After how many seconds will the ball pass the top of the building on its way down?

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