Same as Fig. 3, but depicting the ratio of HC₃N/N₂H⁺ and the fractional abundance of HC₃N and N₂H⁺ with respect to H₂ at six different radii (10² AU, 10³ AU, 7 × 10³ AU, 10⁴ AU, 5 × 10⁴ AU, and 10⁵ AU) from the center using model 4 (left panels) and model 6 (right panels). The results at r = 10² AU, 10³ AU, 7 × 10³ AU, and 10⁴ AU during the HMSC stage in model 4 completely overlap because of the large r_in > 10⁴ AU.