(a) Calculate the amount of fissions required in \({ }^{235} \mathrm{U}\) to produce \(1 \mathrm{~W}\).

(b) Calculate the fissions required in individual fissile species to produce an assembly power of \(500 \mathrm{~kW}\), where fission contribution is \(70 \%\) from \({ }^{235} \mathrm{U}\) and \(30 \%{ }^{239} \mathrm{Pu}\) (Assume fission in a \({ }^{235} \mathrm{U}\) atom gives \(200 \mathrm{MeV}\) and that in \({ }^{239} \mathrm{Pu}\) gives \(197 \mathrm{MeV}\) ).