As an object moves from point A to point B only two forces act on it: one force is nonconservative and does + 40 J of work, the other force is conservative and does +60 J of work. Between A and B, a. The potential energy of the object increases, mechanical energy decreases. b. The potential energy of the object decreases, mechanical energy decreases. c. The potential energy of the object decreases, mechanical energy increases. d. The potential energy of the object increases, mechanical energy increases.