A piece of equipment has a first cost of $180,000, a maximum useful life of 7 years, and a market (salvage) value described by the relation S = 120,000 - 11,000k, where k is the number of years since it was purchased. The salvage value cannot go below zero. The AOC series is estimated using AOC = 60,000 + 8,000k. The interest rate is 11% per year. Determine the economic service life and the respective AW. The economic service life is 7 year(s) and the AW value is $ 86,698.5