Louis has two sets of two gears (Set A and Set B) that he is using to build two different machines. He has all the gears laying out separately, as shown in the diagram above. Then he puts the gears into the machines so that the gears in Set A are touching each other and the gears in Set B are touching each other. Use the information in the diagram to answer the question. After the gears have been touching for a while, which of the two bottom gears will be cooler, and why? *