(a) $\pt$-differential invariant cross sections of electrons from beauty and from charm hadron decays. The error bars (boxes) represent the statistical (systematic) uncertainties. The solid (dashed) lines indicate the corresponding FONLL predictions (uncertainties). Ratios of the data and the FONLL calculations are shown in (b) and (c) for electrons from beauty and charm hadron decays, respectively, where the dashed lines indicate the FONLL uncertainties. (d) Measured ratio of electrons from beauty and charm hadron decays with error boxes depicting the total uncertainty.