If a body moves in a straight line according to the law s = 24t + 3t2 - t3 , where s is the distance measured in meters from the origin and t is the time in seconds after it starts to move, calculate the body's velocity as a function of time. A. V = 30t - t2 B. V = 24 + 6t - 3t2 C. V = 24 + 3t - t2 D. V = 30t - 3t2