  We modeled the V-band light curve of beta Lyrae with two stellar components
plus an optically thick accretion disc around the gainer assuming a
semidetached configuration. We present the results of this calculation, giving
physical parameters for the stars and the disc, along with general system
dimensions. We discuss the evolutionary stage of the system finding the best
match with one of the evolutionary models of Van Rensbergen et al. According to
this model, the system is found at age 2.30E7 years, in the phase of rapid mass
transfer, the second one in the life of this binary, in a Case-B mass-exchange
stage with dM/dt = 1.58E-5 Msun/year. This result, along with the reported rate
of orbital period change and observational evidence of mass loss, suggests that
the mass transfer in beta Lyrae, is quasi-conservative. The best model
indicates that beta Lyrae finished a relatively large mass loss episode 31400
years ago. The light curve model that best fit the observations has inclination
angle i = 81 degree, M1 = 13.2 Msun, M2 = 3.0 Msun, R1 = 6.0 Rsun and R2 = 15.2
Rsun. The disc contributes 22% to the total V-band light curve at quadrature,
has a radius of 28.3 Rsun and the outer edge thickness is 11.2 Rsun. The light
curve model is significantly better with two bright regions in the disc rim
with temperatures 10% and 20% higher than the disc outer edge temperature. We
compare our results with earlier studies of this interacting binary.
