A batch sedimentation centrifuge has a diameter of $600mm$ and a height of $300mm.$ It is used to separate $25$ liters of an aqueous slurry containing suspended solids of average particle size $2m$ and density $=2600kg*m^3.$ The bowl is rotated at $1000rpm.$ Find the time required to free the liquid from solid impurities. Compare with the time it would take for these particles to settle by gravity $($assuming Stokes law is valid$)$ in that same bow$1.$