Simulated data from RADMC-3D (in black), with the fit CASSIS model in red and with T_ex fixed at 150 K. The upper energy levels are printed on the top right of each panel. The dotted green lines mark the transition frequency of each line. This is for the fiducial envelope-only low-mass model (L = 8 L_⊙, M_E = 1 M_⊙ with low-millimeter opacity dust; see Figs. B.2–B.4 for other fitting examples).