Equipment Replacement. Rodney Company purchased a machine five years ago for $30,000. It had an estimated useful life of ten years with no salvage value. Operating costs are $12,000 per year. The machine could be disposed of today for $5,000. A new machine with a five-year life and no salvage value at the end of five years could be bought today for $35.000. Its operating costs are estimated at $8,000 per year. Determine, for the next five years, the relevant cost difference between keeping the old machine and buying the new one.