Observed relation between galaxy mass and metallicity, [Z/X] for local E- and S0-type galaxies. The [Z/X] data adopted from Arrigoni et al. (2010) are shown as crosses. The mean and standard deviation derived from the data are given as the solid and the dotted lines (see Sect. 2). Modeled stellar-mass-weighted [Z/X] of galaxies at 14 Gyr with a given SFT, t_sf (0.1, 0.25, or 0.5 Gyr), accumulated star formation fraction, f_st (0.5, 0.9, or 1.3), and SFR, SFR (10, 100, or 1000 M_⊙ yr⁻¹), assuming the invariant canonical gwIMF, are plotted with coloured filled circles. The results are shown when varying only one of the above parameters in comparison with the black filled circles.