Water at $25C$ flows at $5f\frac{t}{s}$ inside a straight cylindrical tube made of benzoic acid, with a $1-$in$.$ inside diameter. If the tube is $20ft$ long, estimate the mixing$-$cup average concentration of benzoic acid in the water leaving the tube. The Schmidt number for these conditions is $Sc=970$ and the solubility of benzoic acid in water is $2\mathrm{.}5k\frac{g}{m^3}.$