Steps taken to correct for the poor initial model fit caused by the RGS and EPIC-PN cross calibration issue (see Appendix B for details). Top: The ratio between the data and model was used in the KNAK model (λ_N and T_N) for the correction. Bottom: The EPIC-PN spectrum between 6 - 36 Å with the two models on top. The KNAK corrected model was fitted to the data here. In Obs 1 (left) green is the initial model from Paper III and blue is the corrected model; in Obs 2 (right) pink and purple are the initial and corrected models, respectively. The KNAK component only works for a wavelength grid, and therefore the units of this figure are in Angstroms rather than keV.