The protein apotransferrin binds two Fe(III) ions for cell transport. Consider when a 2.00 mL solution of apotransferrin is titrated with 135 ?L of a 1.93 M Fe(III) solution. The initially colorless solution turns red, and the color change can be measured with a spectrophotometer. First, explain why there is a difference in spectrophotometric response during titration before and after the equivalence point by placing the statements below into the appropriate categories?