5. Uranium-235 is fissile and can be used for nuclear bombs. However, it must have a purity of 80% over uranium-238. Uranium-235 has an abundance of .720% while uranium-238 has an abundance of 99.274%. To purify uranium-235, the mixture of isotopes is turned into UF6 and subjected to effusion (diffusion). What is the ratio of rates for effusion of uranium-235 to uranium-238?