Average of relative $\Dzero$, $\Dplus$ and $\Dstar$ yields as a function of the relative V0A multiplicity, $\Nvzero$, measured at $2.8 < \eta < 5.1$ The relative yields are presented in the top panels with their statistical (vertical bars) and systematic (boxes) uncertainties, apart from the uncertainty on the B feed-down fraction, which is drawn separately in the bottom panels The position of the points on the abscissa is the average value of $\Nvzero \big/ \langle \Nvzero \rangle$ For some $\pt$ intervals the points are shifted horizontally by $1.5\%$ to improve the visibility The dashed lines are also shown to guide the eye, a diagonal on (a) and a constant on (b)