Henry bought 3 sets of pencils. After he bought the pencils, his account balance showed a change of -$30.63. What would have been the change to Henry's account balance had he only bought 1 set of pencils? Select one:
a. -$10.21
b. $10.21
c. $10.20
d. -$10.20

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?