71. Rectilinear Motion The distance s (in meters) that an object in rectilinear motion moves in time t (in seconds) is
s = f(t) = t^2 - 6t.
(a) Find the average velocity of the object from 0 to 5 seconds.
(b) Find the velocity at t = 0, at t = 5, and at any time t.
(c) Find the acceleration at any time t.