$($b$)$ A settling chamber is to be use to collect particles of $15$ micron dia., density $\backslash$rho $\_($p$)=2000$k$($g$)/($m$^(3))$ from a stream of $10($m$^(3))/($s$)$ of standard air. The chamber is to be $1\mathrm{.}5$ m wide, $1\mathrm{.}5$m high with $9$ trace including bottom. Determine the length of settling chamber required to achieve $99\%$ efficiency. Also find length required to achieve for $99\mathrm{.}9\%$ efficiency. What would be the efficiency of $25$ micron size particles for first length?