Sedimentation$/$Centrifugation Problem:

You are using a $5$ meter tall sedimentation tank to collect plastic particles suspended in water. The average diameter of the particles is $5$E$-4$ meters, and the density of the sand is $1100$ kg$/$m$^3.$ The viscosity and the density of water are $0\mathrm{.}001$kg$/($m$*$second$)$ and $1000$kg$/$m$^3.$ You can assume the sand particle is in a diluted system, reach the terminal velocity instantaneously, and the gravitation acceleration is $9\mathrm{.}8$m$/$s$^2.$

How long does it take for a sand particle to settle from the top to the bottom of the sedimentation tank?