Predicted numbers of 7 <  z <  9 quasars as a function of (a) redshift and (b) J magnitude, determined by integrating the QLF over the selection functions presented in Fig. 8, and assuming an area of 15 000 deg². Blue: Euclid data only. Red: Euclid O band replaced with ground-based optical data. Solid lines k = −0.72. Dashed lines k = −0.92. The additional black dotted curve on the right-hand panel indicates the estimated number of contaminants selected as quasar candidates as a function of magnitude, assuming ground-based optical data, and so should be compared to the red curves, labelled.