Merger rate of MBHBs detected by LISA with S/N > 7. Each panel corresponds to merged binaries with different total mass (M_Bin). Blue lines show the predictions of the Fiducial model, while orange lines show those of the Off-center model. Pale lines represent the merger rates related to merging binaries with mass ratio q > 0.05 is assumed. The results were produced with L-GalaxiesBH applied in the Millennium-II simulation. The numbers inside each panel correspond to the integrated merger rate with all and mass-cut (q) MBHs in a given mass bin.