Probability distributions of the A and B parameters of the c − M relation Eq. (9) calculated with LIRA, for the full sample (top) and for the subsample of clusters at z ≥ 0.7 (bottom). The relations are normalised at the median redshift of the sample considered (0.59 and 0.80, respectively). The confidence regions are defined as in Fig. 7. The coloured symbols show the estimates of the parameters from simulations by P12, DM14, and DK15 evaluated at the quoted redshift. The green contour shows the constraints from Sereno & Covone (2013) at 1σ.