Air expands adiabatically in a piston-cylinder assembly from an initial state where p = 100 lbf/in.2, v = 3.704 ft/lb, and T = 1000 R, to a final state where p2 = 60 lbf/in. The process is polytropic with n = 1.4. The change in specific internal energy, in Btu/lb, can be expressed in terms of temperature change as Au= (0.171)(T2-T1). Determine the final temperature, in R. Kinetic and potential energy effects can be neglected. T2= R