In a recent paper the probability of forming a ring in vitreous B₂O₃ was evaluated using the stochastic matrix method, as a description of the growth process of a solid. In this work we generalize this method for the same substance introducing a probabilistic cut-off temperature and find a theoretical Vogel-Fulcher-Tamman-like equation for the average relaxation time (or viscosity) of the strong-glass-forming liquid. We take the average relaxation time to be inversely proportional to the probability of forming a ring, calculated for a large number of steps of growth. We also use the temperature derivative method to recognize the functional dependence of the relaxation time.