Relations between the optical energy (time × luminosity) of the optical plateau end (blue dots) and of the peak (black dots) and the 15–150 keV BAT energy (top) and the isotropic prompt emission energy (bottom). Dashed line: best-fitting power-law model obtained accounting for the sample variance (D’Agostini 2005). Gray area: the 68% confidence region around the best fit. The results of the fit are listed in Table 2.