Please solve and show step ill give a good rate if its right

A word-processor was bought two years ago for $22 000. At the time, the machine was expected to last six years and to have operating costs of $7200 the first year, increasing by $300 per year thereafter. The salvage value at the end of the sixth year is assumed to be zero. Another company is presently offering a competitive machine for $16000; they will give $10 000 for the one in use as trade-in value. Although the book value of the old machine is $14 167, this offer of $10 000 is thought to be fair, since the technical obsolescence of the current system would make it very difficult to get a better offer. For this reason, it is believed that the salvage value of the current machine will decrease by $2500 per year over the next four years. The new machine is expected to last four years and to have operating expenses of S6500 per year After four years, its salvage value will be zero. If the MARR is 15%, should the machine be changed? If so, when? Ans. 10.16 The old machine's current market value (salvage value) is $10 000; its economic life is found as 4 more years, with EUACod(4) $11700.59. The new machine also has an economic life of 4 years, with EUACnew(4)= $12 104.32. Thus, the old machine should be kept for four more years