Afield is 240ft by 100 ft, part of the field is torn up. the new field is 1/2 the size of the old one. how wide is the walkway?

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?