Two perfect monoatomic gases at absolute temperatures ${\mathrm{T}}_1 \mathrm{and} {\mathrm{T}}_2$ are mixed. There is no loss of energy. The masses of the molecules are ${\mathrm{m}}_{\mathrm{l}} \mathrm{and} {\mathrm{m}}_2$.The number of molecules in the gases are ${\mathrm{n}}_1 \mathrm{and} {\mathrm{n}}_2$.The temperature of the mixture is

• A

  ${\mathrm{T}}_1 + {\mathrm{T}}_2$

• B

  $\frac{{\mathrm{T}}_1+{\mathrm{T}}_2}{2}$

• C

  $\frac{{\mathrm{n}}_1{\mathrm{T}}_1+{\mathrm{n}}_2{\mathrm{T}}_2}{{\mathrm{n}}_1+{\mathrm{n}}_2}$

• D

  $\frac{{\mathrm{n}}_1{\mathrm{T}}_1-{\mathrm{n}}_2{\mathrm{T}}_2}{{\mathrm{n}}_1+{\mathrm{n}}_2}$