A ball is thrown downward with a speed of 8 ft/s from the top of a 66 ft tall building. After t seconds, its height above the ground is given by s(t) = −16t2 − 8t + 66. (a)
Determine how long (in s) it takes for the ball to hit the ground.

(b)
Determine the velocity (in ft/s) of the ball when it hits the ground.