4. A piston/cylinder device with a set of stops contains 10 kg of refrigerant-134a. Initially, 8 kg of the refrigerant is in the liquid form, and the temperature is -10°C. Now heat is transferred slowly to the refrigerant until the temperature of the system reaches 60°C at which the piston is touching the stops and the volume is 0.5 m³. a) Show these processes with the vapor dome on a p-v and T-v diagrams. b) Find the change in the internal energy, in kJ, from the initial state to the instant the piston hits the stops. c) Determine the work done, in kJ, during the entire process.