You plan to purchase a car for $28,000. Its market value will decrease by 20% per year. You have determined that the IRS-allowed mileage reimbursement rate for business travel is about right for fuel and maintenance at $0.485 per mile in the first year. You anticipate that it will go up at a rate of 10% each year, with the price of oil rising, influencing gasoline, oils, greases, tires, and so on. You normally drive 15,000 miles per year. What is the optimum replacement interval for the car? Your MARR is 9%.