PLZZ HU In a group of 100, each a Borg or a Corg, every Borg has 2 Corg friends and no Corg has more than 1 Borg friend. If exactly 13 Corgs have no Borg friends, then how many Corgs are in the group?

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?