An absorbance of 0.86 corresponds with 1.7 mg substance X. The volume was 500 µl
(0.5 ml), so we get a concentration of 3.4 mg/ml. Sounds good. Checking the other
readable tube, absorbance of 0.12 indicates that the tube contained 0.20 mg substance
X. The volume was 50 µl (0.050 ml). The concentration should be 0.20 mg/0.050 ml =
4.0 mg/ml. Which result do we use, or do we take an average?