Air at 2900 R, 435 psia enters a turbine operating at steady state and expands adiabatically to the exit, where the temperature is 1500 R. If the isentropic turbine efficiency is 90%, determine
(a) the pressure at the exit (psia),
b) the work developed, in Btu per lbm of air flowing.
Assume ideal gas behavior for the air and ignore kinetic and potential energy effects.