We have two urns A and B. Urn A contains 4 red balls and 3 blue balls. Urn B is empty. We randomly draw two balls X1 and X2 without replacement from urn A and put them into urn B. Then we draw two balls Y1 and Y2 randomly with replacement from urn B. 1. Given that Y1 and Y2 have the same color, what is the probability that X1 and X2 have the same color