Henry makes orange squash with 3 parts squash to 5 parts water. Paul makes orange squash with 4 parts squash to 12 parts water. Whose squash will taste sweeter?

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?