b$.$ A gravity classifier shown in FIGURE Q$1$ is used to cla sify the solid particles into two ranges of $200-350m$ and $350-500m$ ivin a gas flowing at a rate of $1\mathrm{.}8\frac{m^3}{s}.$ The density of the particles is $1800k\frac{g}{m^3}.$ The density of the gas is $1\mathrm{.}2k\frac{g}{m^3}$ and its viscosity is $1\mathrm{.}8{10}^{-5}k\frac{g}{m}\frac{?}{s}.$ Estimate the dimensions of the classifier assuming the height $(H)$ to breadth $(B)$ ratio is $2$:$1.$w