A turbine operating at steady state receives air at a pressure of Pi= 3.0 bar and a temperature of T = 390 K. Air exits the turbine at a pressure

of p2 = 1.0 bar. The work developed is measured as74 kJ per kg of air flowing through the turbine. The turbine operates adiabatically, and changes in kinetic and potential energy between inlet and exit can be neglected. Using the ideal gas model for air, determine the isentropic turbine efficiency. \eta_{\mathrm{t}}=\frac{\dot{W}_{\mathrm{cv}} / \dot{m}}{\left(\dot{W}_{\mathrm{cv}} / \dot{m}\right)_{\mathrm{s}}}=0.70(70 \%)