2. A friend rolls two dice and tells you that there is at least one 6. What is the probability the sum is at least 9?

7. Two events have P(A) = 1/4, P(B|A) = 1/2, and P(A|B) = 1/3. Compute P(A B), P(B), P(A B).

9. Suppose we draw two cards out of a deck of 52. Let A = "the first card is an Ace," and B = "the second card is a spade." Are A and B independent?

11. Nine children are seated at random in three rows of three desks. Let A = "Al and Bobby sit in the same row," B = "Al and Bobby both sit at one of the four corner desks." Are A and B independent?