17. Event A has probability 0.5. Event B has probability 0.6. Which of the following must be true? a. A and B are disjoint. b. A and B must include all possible outcomes in the sample space. c. The probability that A does not occur is 0.5. d. All of the above. 18. An assignment of probability must obey which of the following? a. The probability of any event must be a number between 0 and 1, inclusive. b. The sum of all the probabilities of all outcomes in the sample space must be exactly 1. c. It must obey the addition rule for disjoint events. d. All of the above. Use the following statement to answer the questions 19 and 20