The binding energy B(A,Z) of an atomic nucleus of mass number A, atomic number Z, and number of neutrons N = A-Z, can be expressed as
\[ B(A,Z) = a_1 A - a_2 A^{2/3} - a_3 \frac{Z^2}{A^{1/3}} - a_4 \frac{(A-2Z)^2}{A} \]
where \(a_1, a_2, a_3\), and \(a_4\) are constants of appropriate dimensions.
Let \(B(A, Z')\) be the binding energy of a mirror nucleus (which has the same A, but the number of protons and neutrons are interchanged).
Then, at constant A, \([B(A,Z) - B(A,Z')]\) is