Top panel: K-amplitudes of grid points plotted against their y-values sorted by their x-values. Middle panel: same as the upper panel but for the orbital phases with the highest blueshift. The values corresponding to the observed emission lines are marked by horizontal lines. Bottom panel: line formation sites combining information from the two upper panels (dots with error bars). The bottom panel also shows (dotted) curved contours with constant K-values (200, 300, 400, and 500 km/s increasing from the WR surface) and radial (dotted) contours with the constant bluest phases ϕ (from 0.3 to 0.7).