Consider an air-standard Brayton cycle with adiabatic compressor and turbine, and a regenerator, as shown in the figure. Air enters the compressor at $100 \mathrm{kPa}$ and $300 \mathrm{~K}$ and exits the compressor at $600 \mathrm{kPa}$ and $550 \mathrm{~K}$. The air exits the combustion chamber at $1250 \mathrm{~K}$ and exits the adiabatic turbine at $100 \mathrm{kPa}$ and $800 \mathrm{~K}$. The exhaust air from the turbine is used to preheat the air in the regenerator. The exhaust air exits the regenerator (state 6) at $600 \mathrm{~K}$. There is no pressure drop across the regenerator and the combustion chamber. Also, there is no heat loss from the regenerator to the surroundings. The ratio of specific heats at constant pressure and volume is $c_{p} / c_{v}=1.4$. The thermal efficiency of the cycle is $\%$ ________ (answer in integer).
