6. (15 points) A piston-cylinder system containing nitrogen, N2, undergoes a Carnot power cycle between two thermal reservoirs at 27 °C and 477 °C, respectively. The isothermal expansion process is

accompanied by the 55 kJ heat transfer from hot reservoir to N2. The volume and pressure of the system after the isothermal expansion process are 1 m’ and 0.6 MPa, respectively.If N2 is considered as an ideal gas at these conditions, please determine: (6a). (3p) The thermal efficiency of this power cycle; (6b). (4p) The heat rejected to cool reservoir; (6c). (4p) The work produced during this cycle. (6d). (4p) The boundary work during the isothermal expansion process, and the volume and pressure at the beginning of the isothermal expansion;