d
$n_{1}=4, n_{2}=\frac{1}{2}$
$\gamma_{1}=\frac{3}{5}$ (for monatomic gas)
$\gamma_{2}=\frac{67}{5}$ (for diatomic gas)
$\frac{n_{1}+n_{2}}{\gamma-1}=\frac{n_{1}}{\gamma_{1}-1}+\frac{n_{2}}{\gamma_{2}-1} \Rightarrow \frac{4+0.5}{\gamma-1}=\frac{4}{\frac{5}{3}-1}+\frac{1 / 2}{\frac{7}{5}-1}$
$\Rightarrow \frac{4.5}{\gamma-1}=\frac{12}{2}+\frac{5}{4}=\frac{29}{4} \Rightarrow \frac{\gamma-1}{4.5}=\frac{4}{29}$
$\Rightarrow \gamma-1=\frac{4 \times .4 .5}{29}=0.62 \Rightarrow \gamma=1.62 .$