A class with n kids lines up for recess. The order in which the kids line up is random with each ordering being equally likely. There are three kids in the class named John, Betty, and Mary. The use of the word "or" in the description of the events, should be interpreted as the inclusive or. That is "A or B" means that A is true, B is true, or both A and B are true. Give an expression for each of the probabilities below as a function of n. Simplify your final expression as much as possible so that your answer does not include any expressions of the form (). (a) What is the probability that Betty is first in line or Mary is last in line? (b) Explain the method used to calculate probability.