Two small spherical metal balls, having equal masses, are made from materials of densities $\rho_{1}$ and $\rho_{2}\left(\rho_{1}=8 \rho_{2}\right)$ and have radii of $1 \mathrm{~mm}$ and $2 \mathrm{~mm}$, respectively, they are made to fall vertically (from rest) in a viscous medium whose coefficient of viscosity equals $\eta$ and whose density is $0.1 \rho_{2} .$ The ratio of their terminal velocities would be, (1) $\frac{79}{36}$ (2) $\frac{79}{72}$ (3) $\frac{19}{36}$ (4) $\frac{39}{72}$