If 2 moles of diatomic gas and 1 mole of monatomic gas are mixed, then the ratio of specific heats for the mixture is

μ1=1,γ1=5/3 (for monatomic gas) and μ2=2,γ2=7/5 (for diatomic gas).From formulaγmixture =μ1γ1γ1−1+μ2γ2γ2−1μ1γ1−1+μ2γ2−1=1×5353−1+2×7575−1153−1+275−1=52+732+5=1913