What is the measure of

Me n o w. i need t h i s. 10 points

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?

Which of the following can be used to explain a statement in a geometric proof?