7. On Planet X, the position function of a free-falling object is given by: s(t) = -4t' + 12t + 112 where s is measured in meters and t is measured in seconds. (a) Determine the velocity function for the object. (b) Determine the gravitational acceleration of Planet Z. Be sure to include units. (c) Find the average velocity of the object on the interval [3, 6]. Be sure to include units. (d) Find the velocity of the object at impact. Be sure to include units