Left panel: number of RSGs as a function of luminosity in a region with constant star formation rate (see text). Numbers are normalized to the model with 9  M_⊙. Dots indicate the values obtained for the models with 9, 15, 20, and 25  M_⊙ from left to right. Right panel: radii of various stellar models during the RSG phase (Log T_eff< 3.6) as a function of the luminosity. The shaded area indicates the region covered by the models with different initial masses, rotations, and mass-loss rates. The 25 times enhanced, rotating 15  M_⊙ is the only model that evolves out of this region. The initial mass is indicated at the lowest luminosity predicted by the models for this mass.