Yellowjacket, Inc., a large textile company, is trying to decide how long it should retain one of its machines used in the sludge dewatering processes. The machine currently is estimated to have a $35,000 market value and a future market value of $18,000 next year, decreasing $1700 per year over its remaining maximum useful life of 8 years. The operating cost is expected to be $5500 next year, increasing by $450 each year thereafter. If the company's MARR is 15% per year, what is the economic service life of this asset?