The diagrams below represent rock layers found in two different locations by two different scientists. The scientist at location X used letters to label his rock layers, while the scientist at location Y used roman numerals to label her layers. Examine these diagrams and then answer the question that follows. The scientists both used the same colors and patterns to represent different types of rocks. They also used the same set of black-and-white symbols to represent specific types of fossils in the layers. By correlating layers based on fossils and rock types, the two scientists have discovered that certain rock layers are present in both locations.

Which layers are the same?