Thermodynamics: isentropic efficiency and ideal gas model

[jofree87]

Air at 1175 K, 8 bar enters a turbine operating at steady state and expands adiabatically to 1 bar. The isentropic turbine efficiency is 92%. Employing the ideal gas model with k=1.4 for the air, determine (a) the work developed by the turbine, in kJ per kg of air flowing, and (b) the temperature at the exit, in K. Ignore kinetic and potential energy effects.

The answers my professor provided are W = 486 kJ/kg, and T₂ = 691 K

I found a solution (attached below) on another website that comes up with different answers. The work on the solution looks to be correct, but why do the answers differ? Which answers are correct?

 

[nwkid]

maybe the tables used for finding enthalpy from temperature is different. are you sure about the credibility of the image? the guy has the units of temperature wrong ( mayb just a silly mistake).