Light curves A and B from Fig. 1 have been merged, with light curve A as reference, after shifting light curve B by the measured time delay of Δt = −20.5 days and subtracting the differential extrinsic variability from A. M_A(t) sampled at the epochs t_i and M_B(t) sampled at the epochs t_i + Δt are connected by red and blue lines, respectively. M(t) sampled at the epochs t_i and t_i + Δt are connected by black lines. The optimum free parameters for this pair of light curves were found to be δ = 3.1 days and s = 139.0 days. The magnitudes at those epochs corresponding to maximum absolute values of and have been circled. The negative value of time delay implies that light curve A leads light curve B. The magnitudes are shown without error bars for convenience of display.