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Apply: fossils and rock layers

Problem

The diagrams below show the sedimentary rock layers found at two different locations 20km apart. Letters A, B, and C represent different index fossils present in the layers.
A geologic cross section shows 2 rock columns, each with 3 horizontal rock layers. Starting from the surface and going down on the left column, the layers are: Layer 1. This layer contains no index fossils. Layer 2. This layer contains index fossil A. Layer 3. This layer contains index fossil B. Starting from the surface and going down on the right column, the layers are: Layer 4. This layer contains index fossil B. Layer 5. This layer contains index fossil C. Layer 6. This layer contains no index fossils.
Which two layers are approximately the same age?
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