A comparison of the deprojected Chandra (blue) and the XMM-Newton MOS1 (black), MOS2 (red), and PN (green) spectra of the innermost shell; the most important emission lines have been marked. The Chandra spectrum has been scaled up by a factor of five for viewing purposes. The inset shows the zoomed-in spectra around the Ar line. It can be seen that a slight over/underestimation of the continuum in the broad-band fit can lead to an under/overestimation of the abundances, especially for the weak lines. It is also clearly seen that the XMM-Newton spectra around the high-energy lines (Ar, Ca and Fe-K) are very noisy and are not as resolved as in the Chandra spectrum and therefore the XMM-Newton spectra are not found suitable for the narrow-band analyses.