Consider a combined gas-steam power cycle. For the topping cycle is a simple Brayton cycle, air enters the compressor at 15C at a rate of 10kg/s and the gas turbine at 950C. The bottoming cycle is a reheat Rankine cycle between the pressure limits of 6MPa and 10kPa. Steam is heated in a heat exchanger at a rate of 1.15kg/s by the exhaust gases leaving the gas turbine and the exhaust gases leave the heat exchanger at 200C. Steam leaves the high-pressure turbine at 1.0MPa and is reheated to 400C in the heat exchanger before it expands in the lowpressure turbine. Assuming 80 percent isentropic efficiency for the compressor, pump and turbines. a. Investigate the effect of changing the gas turbine exhaust pressure on the cycle performance. b. Determine the optimum pressure (from part a) and the corresponding net power output and efficiency