c
$\mathrm{f}_1=3, \quad \mathrm{f}_2=5$
$\mathrm{n}_1=3, \quad \mathrm{n}_2=2$
$\mathrm{f}_{\text {mixture }}=\frac{\mathrm{n}_1 \mathrm{f}_1+\mathrm{n}_2 \mathrm{f}_2}{\mathrm{n}_1+\mathrm{n}_2}=\frac{9+10}{\mathrm{f}}=\frac{19}{5}$
$\gamma_{\text {mixture }}=1+\frac{2 \times 5}{19}=\frac{29}{19}=1.52$