4. (20 points) A gas within a piston-cylinder assembly undergoes a thermodynamic cycle consisting of the following three processes: Process 1 2: Compression with PV= constant; from Pl=1 bar, Vl=1.6m3 to V2=0.2m3;U1=U2. Process 2 3: Constant pressure to V3=Vl. Process 31 : Constant volume. U1U3=3549kJ. There are no significant changes in the kinetic energy and potential energy. (4a). (5p) Please sketch the cycle on a PV diagram. (4b). (5p) Please calculate the boundary work and the net heat transfer during the process 12, in kJ. (4c). ( 5p ) Please calculate the boundary work and the net heat transfer for the process 23, in kJ. (4d). (5p) Please calculate the boundary work and the net heat transfer for the process 31, in kJ