An asset is purchased new for $55,000 and has the following salvage values: EOY1: $41,000; EOY2: $36,000; EOY3: $32,000; EOY4: $27,000; EOY5: $15,000; and EOY6: $2000. Using an interest rate of 9%, the asset's optimal economic is years. At that time the asset's EUAC is expressed to the nearest $100