Top: DEM distribution for the SMM/FCS AR spectrum of 1987 Dec. 13, with the Fe abundance increased by a factor of 3.2 compared to the Asplund et al. (2009) photospheric abundance (as Fig. 1). The points are displayed at the effective temperature. ul indicates an upper limit. The labels indicate the main ion and the wavelength in Å. Bottom: same curve, with the results of the XRT_DEM inversion code (black histogram) and of the Monte Carlo XRT_DEM inversion (grey histograms).