Plot the values of GG Absorbance versus concentration on a spreadsheet or a programmable calculator, and carefully determine the slope of the best straight line fit through the data. The slope values for GG, GR, RG, and RR must be accurately determined because they will enable you to solve for the unknown concentration of your mixture of the two cobalt complexes. CLICK HERE if you would like assistance using an Excel spreadsheet for determining the slope of a best fit line. Enter the value of the slope of A vs. C. This is your effective extinction coefficient for GG.