An ideal-gas mixture consists of 60 percent helium and 40 percent argon gases by mass. The mixture is now expanded isentropically in a turbine from 400°C and 1.2 MPa to a pressure of 200 kPa. The mixture temperature at the turbine exit is

(a) 56°C

(b) 195°C

(c) 130°C

(d) 112°C

(e) 400°C