Hello there folks. So i'm doing some homework, and one of the questions asks for a comparison of the microscopic absorption cross sections of B, Cd, Gd, and Hf with the fission cross section of U-235. I've found the fission cross section in my trusty 17th edition of Nuclides and Isotopes, but the next part of the question confused me. It then asks for the macroscopic cross sections assuming density is derived from the periodic table. I'm not sure how to figure out the micro/macroscopic cross sections. There is only one given value per nuclide. Help?!