The corrosion behavior of Co-Ni binary alloys has not been determined. However, use the electron configuration theory to predict the critical alloy composition for Co-Ni alloys, assuming:

a) Each metal atom contributes one valence electron.
b) The alloy composition is represented by a linear combination of the individual atomic percentages of cobalt and nickel.
c) The electron configuration of cobalt is [Ar] 3d7 4s2.
d) The electron configuration of nickel is [Ar] 3d8 4s2.