b$.$ Suggest how magnetite could be modified by atomic substitution with another first row transition metal cation such that the saturation magnetization is increased to $5\mathrm{.}25\backslash$times $105$A m$-1.($Assume that substituting an Fe ion with another ion from the first$-$row transition elements does not change the lattice constant significantly.$)$ What would then be the saturation flux density of your material?