4. Use the ideas of opportunity cost, marginal analysis, and sunk cost to give advice to the following people: a. When Ursula goes to an all-you-can-eat buffet, she eats so much that she is sick for two days. But she says it's OK, because it didn't cost her anything extra. Your advice? b. Victor is thinking about starting a small business selling baseball caps in the shopping mall. He tells you that if he makes a nancial investment of $10,000 and works full-time for a year, he can earn $20,000 per year. Since the gain of $20,000 exceeds the $10,000 he invests, this seems like a good idea to him. Your advice? c. Xavier works at a U5. post ofce in a large city, which is located in a lovely old building in a prime downtown location. He says that it's a great deal, because the building was bought and paid for many years ago and so it now has zero cost. Your comment? d. Yolanda works for a company that spends $20,000 on surveys to decide whether to launch a new product. Then it decides that it needs to launch the product to earn back the money it spent on the surveys. Your advice? e. Zachariah decides that his favorite food is grapes: therefore, he decides that he will eat nothing but grapes from now on. Your advice