I need help with the bottom 3.

10. [8/17 Points] DETAILS PREVIOUS ANSWERS A ball thrown upward at 24 ft/sec from a platform 16 feet above the ground is s(t) = 16 + 24t - 16t2 feet above the ground t seconds after it has been thrown. (a) Find the velocity and acceleration of the ball as functions of time. v (t ) = -32t + 24 a(t) = 32 (b) How long does it take (in seconds) for the ball to get back to the platform? sec (c) How much time (in seconds) does the ball spend in the air before it reaches the ground? sec (d) What is the ball's velocity (in feet per second) when it hits the ground? ft/sec