why is it important not to leave fingerprints or scratch the sample cells in spectrophotometric measurements?

Which of the following does the reading test of the sat ask you to do ?

Case # 51173878 weighs 814 pounds; case # 51173981 weighs 803 pounds; case # 51174058 weighs 817 pounds; case 51174178 weighs 815 pounds; case # 51174248 weighs 817 pounds; case # 51174495 weighs 781 pounds; case # 51174577 weighs 828 pounds. what are the case #'s of the two cases that weigh the same amount?

+++30 points me in a society that favors economic equity over economic freedom, who would benefit? explain