Top panel: Keplerian rotation vs. distance from the central source for a 10 M_⊙ (blue solid curve) and 20 M_⊙ (green solid curve) protostar. Dashed lines show the expected Keplerian velocity for i equals 10°, 15°, and 90° (blue, green, and red dashed line, respectively). Vertical lines at 0.4 au (dashed) and 2.0 au (solid) are drawn for reference where the lines intersect with the plausible inclination values. Bottom panel: disc temperature vs. distance from the central source for log₁₀ L_* = 3.10 (black dashed curve) and log₁₀L_* = 4.13 (black solid curve). Observed gas temperature range is indicated in purple. Vertical lines at 0.9 au (dashed) and 2.5 au (solid) are drawn for reference where the lines intersect with the plausible values in temperature.