$3(15).$ Beginning in the late $1970$s$,$ methyl tert$-$butyl ether $($MTBE$)$ was used to increase the octane rating of gasoline and to increase its oxygen content so as to improve combustion and reduce air pollution. However since MTBE is water soluble, serious groundwater pollution resulted from leakage of MTBE$-$containing gasoline from buried storage tanks at refilling stations and other locations. Stripping of the contaminated water with air emerged as a solution to bring the contamination level down to the drinking water standard mol fraction of $2\mathrm{.}650{10}^{-9}.$ If you have a $5-$stage system and the need to treat $15,000$lbmo$\frac{l}{h}$ of water contaminated with MTBE at a mol fraction of $3\mathrm{.}500{10}^{-6},$ what must the air flow rate be in Ibmol$/$h$?$ You may assume a temperature of $25C$ where the $K$ value is $32\mathrm{.}60.$ Hint: Keep $4$ significant figures. State any additional assumptions made in your analysis.