Operating data are taken on an air turbine. For a particular run, P1 = 8 bar, T1 = 600 K, and P2 = 1.2 bar. However, the recorded outlet temperature is only partially legible; it could be T2 = 318, 348 or 398 K. Which must it be? For the given condition assume that air is an ideal gas with CP = 7R/2