One box containing `1` mole of `He` is `7//3 T_0` and other box containing `1` mole of a polyatomic gas `(gamma =1.33)` at `T_0` are placed together to attain thermal equilibrium. The final temperature `T_f`. Then :
A. `T_(f)=9/13 T_(0)`
B. `T_(f)=13/9 T_(0)`
C. `T_(f)=(T_(0))/2`
D. `T_(f)=3/2T_(0)`