Column density ratios of formamide (top) and methyl cyanide (bottom) to methanol as a function of luminosity for all the models. The solid line shows the weighted mean (by errors) of the log₁₀ of the model points. The gray area presents the weighted standard deviation of the model results. Green shows models with low-millimeter opacity dust, and orange shows those with high-millimeter opacity dust. Empty circles show the models with a disk, and the filled ones present the models without a disk. The purple bar shows one standard deviation below and one standard deviation above the mean of the observational data for low- and high-mass protostars in Nazari et al. (2022a). The horizontal dotted lines show the abundances assumed in the models. The models with non-detection of methanol are not plotted.