The neutron separation energy is defined to be the energy required to remove a neutron from a nucleus. Obtain the neutron separation energy of the nuclei $_{20}Ca ^{41}$ from the following data : $m(_{20}Ca^{40})=39.962591\;u,m(_{20}Ca^{41})=40.962278\;u,m(_{13}Al^{27})=26.981514\;u$

Question

$\begin{array}{1 1} 26.981541\;Mev \\ 56.35\;Mev \\ 28.984 \;Mev \\ 78.678\;Mev \end{array} $