You work as a lab assistant. Each morning you are responsible for grouping the correct number of test tubes for each experiment that will be conducted that day. Today 40 test tubes will be used for 12 experiments. The first two experiments will require 4 test tubes each. Six of the experiments will require 3 test tubes each, and 2 of the experiments will require 2 test tubes each. Each of the two remaining experiments will use exactly the same number of test tubes. Which calculation is appropriate to perform first when determining the number of test tubes that will be used for each of the two remaining experiments?