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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 $9,000. A replacement costs $81,000 with a $10,000 salvage value after 3 years and an operating cost of $26,000 per year. Different vendors have offered $10,000 and $23,000, respectively, for the current system as a trade-in for the replacement machine. At i = 8% per year, perform a replacement study and determine whether the defender should be retained or replaced. According to the replacement study. (Click to select) (Click to select) retain defender select challenger 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 $9,000. A replacement costs $81,000 with a $10,000 salvage value after 3 years and an operating cost of $26,000 per year. Different vendors have offered $10,000 and $23,000, respectively, for the current system as a trade-in for the replacement machine. At i = 8% per year, perform a replacement study and determine whether the defender should be retained or replaced. According to the replacement study. (Click to select) (Click to select) retain defender select challenger