A model rocket is fired vertically upward from rest. Its acceleration for the first three seconds is a(t) = 66 t, at which time the fuel is exhausted and it becomes a freely "falling" body. 15 seconds later, the rocket's parachute opens, and the (downward) velocity slows linearly to -23 ft/s in 5 s. The rocket then "floats" to the ground at that rate.
Determine the position function s and the velocity function v (for all times t).