A closed system consists of a pendulum that is swinging back and forth. If the pendulum's gravitational potential
energy decreases, what else must happen to the energy of the
system?
O A. Its total mechanical energy must decrease.
O B. Its kinetic energy must decrease.
O C. Its kinetic energy must increase.
D. Its total mechanical energy must increase.

Refrigerant-134a flows through a carnot heat pump cycle at 0.5 kg/s. it is known that the maximum absolute temperature in the cycle is 1.1 times the minimum absolute temperature, and the net power input to the cycle is 2.5 kw. if the refrigerant changes from a saturated vapor to a saturated liquid during the heat rejection process, determine the maximum magnitude of the enthalpy of vaporization for this process in kj/kg (with 3 significant figures).