Carlos swam the perimeter of a rectangular pool seven times. if the length of the pool is 21 ft and the width of the pool is 9 ft, how many feet did carlos swim?

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?