In rolling two dice, event X is defined as the outcomes {8, 11}; event Y is defined as the outcomes {2, 9, 4}; and event Z is the set of outcomes whose sum is odd. The probability of rolling a sum of 8 on two dice is 5/36; the probability of rolling an 11 is 2/36; the probability of rolling a 2 is 1/36; the probability of rolling a 9 is 4/36; the probability of rolling a 4 is 3/36; and the probability of rolling an odd number is one-half. What is the probability that neither X nor Y will occur?