Figure of merit values as a function of the bend frequency for M = 10⁸ M_⊙ and R_Edd = 0.1, B, for the better-fitting models with different power law slopes (α_L and α_H, as noted in the title of each panel). Blue dots show the minimum, fom/N, for each value of B, with all other parameters free, corresponding to the second iteration, with a finer grid in the parameters. The horizontal black line marks the lowest fom/N achieved and the grey line marks the level of min(fom)/N + Δ, from which the error bounds were estimated. The value of Δ was obtained for each model, as is described in Sect. 6.1.