Mia bought a 100-pound bag of dog food h he gave his dog the same amount each week the dog food lasted 8weeks how much did He give His dog each week

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?