In part A, a specific mass transfer operation was discussed with one mass transfer theory. The mass transfer operation focused in Part A will be liquid-liquid extraction in packed column where the mass transfer theory used to describe it will be Whitman Two film theory. According to two-film theory, there will be an interface between the heavier liquid and lighter liquid that is fed into the column while two liquid films corresponding to the two liquid phases adhere to the interface. Besides, resistance exists in these two liquid films while the resistance across the interface can be ignored. Molecular diffusion occurs at the interface. After the molecular diffusion happens, the solute is extracted from the feed to the solvent. The heavier liquid initially fed from the top which consists of solute will leave the packed column at the bottom as raffinate while lighter liquid or solvent initially fed from the bottom will leave the column from the top as extract.