18. Given two events A and B with P(A) = 0.4 and P(B) = 0.7, what are the maximum and minimum possible values for P (A B)?

23. A tourist wants to visit six of America's ten largest cities. In how many ways can she do this if the order of her visits is (a) important, (b) not important?

25. A commercial for Glade Plug-ins says that by inserting two of a choice of 11 scents into the device, you can make more than 50 combinations. If we exclude the boring choice of two of the same scent how many possibilities are there?