Radial profile of the systematic error ΔZ/Z for 2A 0335+096. Top and middle panels: results obtained through an individual fit of the MOS and pn spectra of each region are shown, following strategy 1 and 2, respectively. Bottom panel: same profiles are shown, with the MOS and pn spectra of each region considered jointly in the fitting. The weighted averages of the results are shown, together with their 1σ errors, as the pink and the yellow regions for strategy 1 and 2, respectively.