If $1$ mole of an ideal monoatomic gas is mixed with 2 moles of an ideal diatomic gas, what is the temperature of the given mixture, given that the monoatomic gas is at temperature $T_0$ and diatomic gas is at temperature $2T_0$?

Question

$\begin{array}{1 1} 1.33\;T_0 \\ 1.77 \;T_0 \\ 1.5\;T_0 \\ 1.25\;T_0 \end{array}$