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0 . Two identical aqueous solutions containing valuable solute are colored by small amounts of an impurity, to a different extent. The dark solution has a color intensity of 50 units and the light solution has 20 color units, measured on the same arbitrary scale. It is desired to treat an equal amount of light and dark solutions to a color unit of 0.5 . The equilibrium adsorption isotherm on activated carbon is given by Freundlich Equation Y=mX, where n=1 and m=0.005 with Y= color units /kg solution and X= color units adsorbed kg carbon. The color scale is such that colors are additive, i.e., equal weights of solution of color 20 and 50 will give a solution of color (20+50)/2=35. In a single stage process, will it be more economical of carbon to first blend the original solutions and to treat the blend, or treat each separately to color 0.5 and to blend the finished products ? a. blend first, treat later c. both a and b b. treat first, blend later d. none of these