The top cycle of a combined cycle power plant has a pressure ratio of 12. Air enters the compressor at 300 K at a rate of 12 kg/s and is heated to 1300 K in the combustion chamber. The steam in the bottom cycle is heated to 350°C at 10 MPa in a heat exchanger, and after leaving the turbine is condensed at 10 kPa. The combustion gases leave the heat exchanger at 380 K. Assume that all compression and expansion processes are isentropic. Determine the thermal efficiency of the combined cycle.