Measurements of mass spectra of dilepton pairs in the HADES experiment in the energy domain of SIS18 and SIS100 (FAIR, Darmstadt, Germany) are very important for studing the excitation function of the virtual photon radiation from dense nuclear matter. A detail study of this phenomenon in the intermediate mass region (0.14 < M < 0.6 GeV/c2) demands precise measurements of inclusive cross sections of