A differential extractor is being used to extract an amino acid from an aqueous solution $($concentration $=1$ g$/$L$)$ to an organic solvent. The extractor is $1$ m long, the feed flow rate is $0\mathrm{.}01$ m$3/$s$,$ the extracting solvent flow rate is $0\mathrm{.}005$ m$3/$s$,$ the average concentration difference across the stagnant film on the raffinate side is $0\mathrm{.}1$ g$/$L$,$ and the raffinate concentration is $0\mathrm{.}2$ g$/$L$.$ Calculate the mass transfer coefficient on the raffinate side if the interfacial area per unit height of the extractor is $100$ m$2/$m$.$