Evolution of the radius and temperature of the donor. (Up): Evolution of the donor star size with an initial mass of 3.5 M_⊙ in the binary system OGLE-LMC-ECL-14413, with a companion that has an initial mass of 3.3 M_⊙, showing the phases in which cases A, B, and C of RLOF can occur, depending on the age of the system. The inversion of the ¹H/⁴He ratio (X1 stage) is represented by a yellow dot, the mass transfer (E stage) by a blue dot, and the current stage of the system (X2 stage) by a red dot. (Down) Effective temperature T_eff as function of age for OGLE-LMC-ECL-14413. We show that the donor star, after crossing the Hertzsprung gap during the onset the blue loop (Stages C and D), follows an evolutionary track until reaching its current stage (X2 stage) on a thermal timescale. This continues until reaching the final stage of non-optically thick mass transfer (H-stage), stopping shortly before Helium depletion.