Using the concepts of opportunity cost, marginal analysis and sunk cost what advice would you give the following people:

A) Dani loves to eat at the buffet at the casino. She gorges herself so that she is sick for the next two days. She says she does it because it doesn’t cost her anything extra? Your advice?

B) Layne works for a surveying company that spends $20k on surveys to decide whether or not to launch a new product or service. Then the company decides it needs to launch the product or service to earn back the monies spent on the survey. Your advice?

C) Andrea decides her favorite food is In-N-Out Double Double cheeseburgers, therefore, she decides that she will eat nothing but Double Doubles from here on out. Your advice?

D) A student has a car to sell. The student spent $500 on tires in the last year. The student could sell the car for $3000, however, if the student upgraded the car stereo he could sell the car for $3,500. The upgrade would cost $350. Should the student sell the car as is, or upgrade the stereo?

E) Brandy is at a vacation resort in San Diego where a kayaking trip in the harbor was included in the price for the room. Brandy is deathly afraid of kayaking in the ocean because she gets sick. But she thinks because she has paid for it, she should go kayaking. Your advice?