A student analyzes a copper-based alloy known to contain \(\text{Cu}\) and exactly one additional metal, \(X\), which is either \(\text{Co}\) or \(\text{Ni}\). Because the valence-region peaks of the metals overlap, the student examines resolved core-level peaks that are absent from the spectrum of pure \(\text{Cu}\). Reference data are shown below.

Metal standard	\(E_{3p}\) \((\text{eV})\)	\(E_{3s}\) \((\text{eV})\)
\(\text{Co}\)	\(59.0\)	\(101.0\)
\(\text{Ni}\)	\(66.0\)	\(111.0\)

The spectrometer may add the same unknown constant offset to every reported binding energy in a spectrum. Tests with standards indicate that alloying changes \(E_{3s}-E_{3p}\) from the pure-metal value by no more than \(0.5\ \text{eV}\). Peak areas also depend on the concentration of each metal and the instrumental response to each subshell. Which additional PES result would be sufficient to identify \(X\) as \(\text{Co}\) rather than \(\text{Ni}\)?