Extended RL relation including the relative Fe II strength, R_Fe II. Left panel: median relation (blue line) is inferred by maximizing the likelihood function. Green lines show 1000 random selections from the parameter distribution. 66 Mg II time-delay measurements are color-coded to depict log R_Fe III according to the color axis on the right. The RMS scatter is 0.28 dex. Right panel: corner plot shows the parameter distributions inferred from the MCMC method. The parameter uncertainties correspond to 16th and 84th percentiles.