In a replacement analysis problem, the following facts are known: initial cost ($12,000), the annual maintenance (none for the first 3 years, $2,000 at the end of the 4th year, $2,000 at the end of the 5th year, increasing $2,500 per year after the 5th year). The salvage value in any year is zero. Assume a 10% interest rate and ignore income taxes. Compute the life for this challenger having the lowest EUAC.