According to one estimate, the first atomic bomb released an energy equivalent to 20 kilotons of TNT. If 1 ton of TNT releases about 4.0 109 J, how

According to one estimate, the first atomic bomb released an energy equivalent to 20 kilotons of TNT. If 1 ton of TNT releases about 4.0 109 J, how much uranium was lost through fission in this bomb? (Assume 208 MeV released per fission.)