The expression 14.99n + 4.99 represents the cost of n CDs. Find the total cost for 3 CDs. Please answer this algebra question. My answer was 49.96 but my homework says it is wrong.

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?