Consider the following costs of owning and operating a car. A $$15,000$ Ford Taurus financed over $5$ years at $10$ percent interest means a monthly payment of $$318\mathrm{.}71.$ Insurance costs $$100$ a month regardless of how much you drive. The car gets $20$ miles a gallon and uses unleaded regular that costs $$3\mathrm{.}05$ per gallon. Finally suppose that wear and tear on the car costs $15$ cents a gallon. Which costs are fixed and which are variable? Why? Explain. Also, in deciding whether to drive from New York to Pittsburgh$($about $1,000$ miles round trip$)$ to visit a friend, which costs would you consider and why?