Show that the thermal efficiency of a combined gas-steam power plant ncc can be expressed as ncc = ng + ns – ngns where ng = Wg/Qin and ns = Ws/Qg, out there thermal efficiencies of the gas and steam cycles, respectively. Using this relation, determine the thermal efficiency of a combined power cycle that consists of a topping gas-turbine cycle with an efficiency of 40 percent and a bottoming steam-turbine cycle with an efficiency of 30 percent.