A closed system executes a reversible cycle 1-2-3-4-5-6-1 consisting of six processes. During processes 1-2 and 3-4 the system receives 1000 kJ and 800 kJ of heat, respectively, at constant temperatures of 500 K and 400 K, respectively. Processes 2-3 and 4-5 are adiabatic expansions in which the system temperature is reduced from 500 K to 400K and from 400K to 300K, respectively. During process 5-6 the system rejects heat at a constant temperature of 300 K. Process 6 - 1 is an adiabatic compression process. Determine the work done by the system during the cycle and the thermal efficiency of the cycle.