Fission of nuclei is possible because the binding energy per nucleon in them

In any fission process the ratio

mass of fission products

mass of parent nucleus

is

Which one of the following pairs of nuclei are isotones ?

In the reaction $${}_1^2$$H + $${}_1^3$$H $$ \to $$ $${}_2^4$$He + $${}_0^1$$n, if the binding
energies of $${}_1^2$$ H, $${}_1^3$$H and $${}_2^4$$He are respectively a, b and c (in MeV),
then the energy (in MeV) released in this reaction is