Consider 2 urns, I and II, each of which contains 1 white and 1 red ball. One ball is drawn simultaneously from each urn and placed in the other urn. Let the probabilities that after n repetitions of this procedure urn I will contain 2 white balls, 1 white and 1 red, or 2 red balls be denoted by pm, qm and rn, respectively. Deduce formulas expressing pn+1, qn+1 and rn+1 in terms of pn, qm and rn Show that pm qm and rn tend to limiting values as n tends to infinity. Interpret these values.