Observed spectrum, PD, and PA predicted by retBB for a = 0.998, M = 21.2 M_⊙, Ṁ = 2.5 × 10¹⁷ g s⁻¹, i = 45° and f_col = 1.5. (a) The red dotted curve shows the spectrum of the direct disk emission. The blue dashed curves from top to bottom show spectra of the first to fourth orders of elastic reflection of the returning radiation. The solid black and green curves show the total spectrum, including single- and multiple-scattering (up to fourth order) of the returning radiation, respectively. (b) and (c) PD and PA, including a single (black solid) or multiple (up to the fourth order; green solid) reflection of returning radiation; blue dashed and red dotted curves show contributions of the first order reflection and direct disk radiation, respectively.