Radial-velocity fit of the synthetic spectrum to the observed He IIλ3813 and He I λ3819 absorption lines of the UVES spectrum with ID 10 (Table 1). The observed spectrum is shown as a solid blue line, our best fitting model as a dotted red line, the unweighted synthetic spectrum of the primary as a dashed black line, and the unweighted spectrum of the secondary as a dotted green line. The observed spectrum is convolved with a Gaussian with a FWHM = 0.2 Å and is corrected for the velocity of the SMC and the barycentric motion. The line identification marks correspond to the wavelengths of the absorption lines in the rest frame.