Terminal velocity

2019 Odisha 1 question

1. Two small spherical metal balls, having equal masses, are made from materials of densities $\rho_1$ and $\rho_2$ ($\rho_1=8\rho_2$) and have radii of 1 mm and 2 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: