Halcrow,Inc., expects to replace a downtime tracking system currently installed on CNC machines. The challenger system has first cost of $70,000, an estimated annual operating cost of $20,000, a maximum useful life of 5 years, and a $10,000 salvage value anytime it is replaced. At an interest rate of 10% per year, determine it's economic service life and corresponding AW value. Work this problem using hand calculator.