Suppose a triangle has two sides of length 2 and 3 and that angle between these two sides is 60 degrees. what is the length of the third side

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?