The first atomic bomb released an energy equivalent of $2.0 \times 10^{1}$ kilotons of TNT. One kiloton of TNT is equivalent to $5.0 \times 10^{12} \mathrm{J} .$ Uranium- 235 releases $3.21 \times 10^{-11} \mathrm{J} /$ atom. What was the mass of the uranium-235 that underwent fission to produce the energy of the bomb?