Line ratio of H₂CO 3_0,3–2_0,2 over 3_2,2–2_2,1 modeled with RADEX. Observed line ratios are shown with a diamond (A), circle (B) and triangle (F) at the best-fit densities derived using the CH₃OH line ratios (see text). Error bars for the uncertainties originate from the line ratio error (21%). Errors on the densities originate from the χ² fitting. Temperatures are 215 K (A), 150 K (B) and 100 K (F).