6-9. DuPont claims that its synthetic composites will replace metals in the construction of future automobiles. “The fuel mileage will double,” says DuPont. Suppose the lighter and stronger “composite automobile” will get 50 miles per gallon of gasoline, and that gasoline costs $3.50 per gallon. The anticipated life of the automobile is six years, i = 10% per year, and annual travel is 20,000 miles. The conventional car averages 25 miles per gallon. (6.4)

a. How much more expensive can the sticker price of the composite automobile be and still have it as an economical investment for a prospective auto buyer? State all important assumptions.

b. What is the trade-off being made in Part (a)?