Sedimentation basin in a water treatment plant is designed for a flow rate of $0.2 \: m^3/s$. The basin is rectangular with a length of $32 \: m$, width of $8 \:m$, and depth of $4 \: m$. Assume that the settling velocity of these particles is governed by the Stokes’ law. Given: density of the particles $=2.5 \: g/cm^3$; density of water $=1 \: g/cm^3$; dynamic viscosity of water $=0.01 \: g/(cm.s)$; gravitational acceleration $=980 \: cm/s^2$. If the incoming water contains particles of diameter $25 \mu m$ (spherical and uniform), the removal efficiency of these particles is
1. $51 \%$
2. $65 \%$
3. $78 \%$
4. $100 \%$