Unfortunately you would likely be in breach of the Copyright in Chapter 3. It seems from your comments that they have made it quite clear that the work has been modified, which presumably includes modifications to Chapter 3. They would then have the copyright in that modified version of chapter 3.
The short answer is that you should not use it as the basis for your further modifications without obtaining permissio. Hopefully, someone reading this thread will be able to point you in the direction of the original text.
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