A rocket is fired vertically with an upward acceleration of

A rocket is fired vertically with an upward acceleration of 20 m/s2. After 25 s, the engine shuts off and the rocket continues as a free particle until it reaches the ground. Calculate
(a) The highest point the rocket reaches,
(b) The total time the rocket is in the air,
(c) The speed of the rocket just before it hits the ground. Take up as the positive direction.