A currently owned welding machine was purchased for $150,000 three years ago by a company. This machine can be sold now for $45,000. If it is, however, kept, it can be remained functional for two more years, and its operating and maintenance cost will be $12,000 in year 1 and $14,000 in year 2. It can be sold for $25,000 (in today's dollar) at the end of year 1 and for $20,000 at the end of the second year. There is a replacement option (challenger) that will cost the company $250,000. This machine can be kept for 6 years and be sold for $35,000 at the end of that useful life. Its annual operating cost will be $15,000 per year (in today's dollar). If the real interest rate is 6% per year and the inflation rate is 3% per year, perform a replacement study and determine whether the current machine (defender) should be retained or replaced right away, and if retained, after how many years to be replaced