Please give me the solution in detail for this question.

Question 1: If a stone is dropped from a cliff that is 200m high, then its height, h, in metres after t seconds is h(t) = 200 - 4.9t. a) Find the stone's velocity at 2 seconds. b) When does the stone have a velocity of 39.2m/s [down]? c) With what velocity will the stone hit the ground