3. Consider an ideal Brayton cycle with two stages of compression and two stages of expansion. Air enters the compressor at 100 kPa ve 27 C, and enters the turbine at 1107 C. A regenerator with 70% effectiveness is also used in the cycle. If the optimum intermediate pressure between the turbine and compressor stages is 800 kPa, determine the thermal efficiency of the cycle. Use variable specific heats.