How could the analysis of the XANES spectrum at the Fe K-edge help identify the iron oxidation state(s) present in CaFeO₃ as discussed in Exercise 8.26?

Data from Exercises 26.

Some formally Fe(IV) compounds, such as CaFeO₃, are believed to contain the iron as a mixture of Fe(III) and Fe(V). Predict the key features of the ⁵⁷Fe Mössbauer spectra of this compound when described as 

(a) CaFe(IV)O₃ 

(b) CaFe(III)_0.5Fe(V)_0.5O₃, assuming iron is in a regular octahedral coordination to oxygen in both descriptions. Could Mössbauer spectroscopy be used to distinguish these two descriptions? CaFeO₃ orders antiferromagnetically at low temperatures and the Mössbauer spectrum at 4 K consists of two overlying, magnetic hyperfine six-line patterns. Which is the best description of the iron oxidation states in CaFeO₃ at this temperature?