I want to know how to solve the question 6.87.i and j

6.87 As input into pricing policy, the owner of an appliance store is interested in the relationship between the price at which an item is sold (retail or sale price) and the customer's decision on whether or not to purchase an extended warranty. The owner has constructed the accompanying table of probabilities, based on a study of 2000 sales invoices. Suppose that one sales invoice is selected at random, with the relevant events being defined as follows: A: The item is purchased at retail price. B: The item is purchased at sale price. C: An extended warranty is purchased. D: An extended warranty is not purchased. Extended warranty Price Purchased (C) Not purchased (D) Retail price (A] 0.21 0.57 Sale price (B) 0.14 0.08