Evolution of the light-echo surface-brightness in the F435W (upper panel), F606W (middle panel), and F814W (bottom panel) filters. Open symbols and full curve: observed light-echo surface-brightness S_B (Col. 6 in Table 1) and its best-fitting model. Filled symbols and dashed curve: the same but for S_B   0.5 (Col. 8 in Table 1). Parameters of the fit can be found in Table 2 middle and bottom rows.