A spherical ball of density $\text{ρ}$ and radius $0.003 \mathrm{m}$ is dropped into a tube containing a viscous fluid, filled up to the $0 \mathrm{cm}$ mark as shown in the figure. Viscosity of the fluid =$1.260 \mathrm{N} {\mathrm{m}}^{-2} {\mathrm{s}}^{-1}$ and its density ${\text{ρ}}_{\text{L}}$ = $\text{ρ}/2=1260 \mathrm{kg} {\mathrm{m}}^{-3}$. Assume the ball reaches a terminal speed by the $10 \mathrm{cm}$ mark. Find the time taken by the ball to traverse the distance between the $10 \mathrm{cm}$ and $20 \mathrm{cm}$ mark. [$\mathrm{g}$ = acceleration due to gravity = $10 \mathrm{m} {\mathrm{s}}^{-2}$^​​ ]