Q$5.(5$ pt$)$ Consider the open trench where wastewater $(200m^3)$ containing toluene in water enters one end of the trench with $2m$ depth and $3m$ width at $293K$ and $1\mathrm{.}0$atm. As the wastewater flows down, the aeration gas strips out the dissolved toluene and transfer it to the surrounding atmosphere. The inlet air flow rate is $0\mathrm{.}15\frac{m^3}{m^3}($water$).$min and the flow rate of liquid is $0\mathrm{.}1\frac{m^3}{s}.$ The mass transfer coefficient $(k_{\text{l}\text{l}\text{c}\text{o}\text{r}\text{n}\text{e}\text{r}})$is $2\mathrm{.}7{10}^{-4}\frac{m}{s}$ and the interfacial area is $18m^2$ toluene $\frac{?}{m^3}$ water. The Henry's law constant for toluene in water is $8\mathrm{.}5$ atm$*\frac{m^3}{k}$gmol. Determine the length required to reduce the toluene concentration from $100$ to $0\mathrm{.}005\frac{g}{m^3}.$