Air enters a gas turbine with two stages of compression and two stages of expansion at $100 \mathrm{kPa}$ and $17^{\circ} \mathrm{C}$. This system uses a regenerator as well as reheating and intercooling. The pressure ratio across each compressor is $4 ; 300 \mathrm{kJ} / \mathrm{kg}$ of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by $20^{\circ} \mathrm{C}$. Determine this system's thermal efficiency. Assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature.