Evolutionary tracks of IMXB with different initial donor-star masses and initial orbital periods in the orbital period vs. donor-star mass (top panel) and the mass-transfer rate vs. donor-star mass (bottom panel) diagram when the surface magnetic field of the donor star B_s = 300 G. The solid, dashed, dotted, and dash-dotted curves represent a donor-star mass of 1.6, 1.7, 1.8, and 1.9M_⊙, respectively. Numbers inside the curves denote the initial orbital periods in units of days. The horizontal line in the top panel corresponds to the observed orbital period of Sco X-1.