4. (12 points) An object moves in a straight line and at any time t, in seconds, after its motion starts, its position s, in meters, is given by s = =t3 - 3t2 + t + 2, The velocity v of the object at any time t is defined by v = = derivative of s with respect to t it while the acceleration a of the object at any time t is defined by a = = = derivative of v with respect to t A. Find the velocity and acceleration of the object at any instant of time f. B. Find the velocity of the object when its acceleration is zero