If three moles of monoatomic gas (γ=5/3) is mixed with two moles of a diatomic gas (γ=7/5), the value of adiabatic exponent γ for the mixture is

If three moles of monoatomic gas $\displaystyle \left(\gamma=\frac{5}{3}\right)$ is mixed with two moles of a diatomic gas $\displaystyle \left(\gamma=\frac{7}{5}\right)$, the value of adiabatic exponent $\displaystyle \gamma$ for the mixture is