An object is moving along a horizontal co-ordinate line according to the formula s(t) = t* -12t3 + 30t2 + 5t, t 2 0, where s(t), the directed distance from the origin, is in feet and time is in seconds. (a) Determine the velocity, v(t), and acceleration, a(t), at time t? (1 mark) (b) When is the acceleration negative