As discussed in the "A Word About . . . Pasteur's Experiments and the van't Hoff-LeBel Explanation", a critical experiment and observation made by Pasteur was that when he dissolved pure forms of the left- and right-handed crystals, he found that each solution was optically active, even though each set of crystals was obtained from crystallization of the racemic acid. The optical rotations of (R,R)- and (S,S)-tartaric acid are provided in Figure 5.14. Predict the specific rotation of a solution that contains 75% (R,R) and 25% (S,S) crystals of tartaric acid.