A turbine operating at steady state receives air at a pressure of P1=3.0 Bars and a temperature T1=390K. Air exits the turbine at pressure of P2=1.0Bars. The work developed by the turbine is measured as 74Kj/Kg of air flowing through the turbine. The turbine operates adiabatically and changes i Kinetic and potential energy between inlet and outlet can be neglected. Using ideal gas model and considering the specific heat variation with temperature, determine the turbine isentropic (adiabatic) efficiency.