Given the high cost of gasoline, automobile owners are constantly searching for ways of economizing on driving expenses. One costly alternative for many persons is to purchase a car which gets significantly better gasoline mileage than does their present car. Chamberlain developed a mathematical formula to calculate how many years a person would have to drive a new car to make the gasoline savings offset the cost of trading in the old car and buying a new one. The variables to be used in this analysis are y = number of years to justify the purchase of a new car, m = gasoline mileage of present car, miles per gallon, n = gasoline mileage of new car, miles per gallon, c = net cost of new car (purchase cost less proceeds from sale of present car), d = average number of miles driven per year, p = gasoline price per gallon. Chamberlain determines this "break-even" period using the general relationship Cost of gasoline = Cost of gasoline + net cost of new car for present car for new car during during break even period break even period fold(y) = fnew(y). Using the variables defined previously, determine the expressions for fold(y) and fnew(y)?
