A piece of equipment has a first cost of $165,000, a maximum useful life of 7 years, and a market (salvage) value described by the relation S = 120,000-19,000k, 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 + 10,000k. The interest rate is 12% per year. Determine the economic service life and the respective AW. The economic service life is years) and the AVN value is $