a$)$ Calculate BE A for $137$Ba$,$ the rarer of the two most common barium isotopes, in MeV$/$nucleon$.($Assume $1$ u $=931\mathrm{.}5$ MeV$/$c$2.$ Enter your answer to at least three decimal places.$)$ MeV$/$nucleon $($b$)$ Calculate BE A for $138$Ba in MeV$/$nucleon$.($Most of barium is $138$Ba$.)$ Note that $138$Ba has even numbers of both protons and neutrons. $($Enter your answer to at least three decimal places.$)$ MeV$/$nucleon Is the BE A of $138$Ba significantly different from that of $137$Ba$?$