A presently owned machine can last 3 more years, if properly maintained at a cost of $15,000 per year. Its AOC is $31,000 per year. After 3 years, it can be sold for an estimated $9000. A replacement costs $80,000 with a $10,000 salvage value after 3 years and an operating cost of $19,000 per year. Different vendors have offered $10,000 and $20,000, respectively, for the current system as trade-in for the replacement machine. At i = 12% per year, perform a replacement study and determine whether the defender should be retained or replaced.