A construction company bought a 180,000 metric ton earth sifter at a cost of $65,000. The company expects to keep the equipment a maximum of 7 years. The operating cost is expected to follow the series described by 40,000  10,000k, where k is the number of years since it was purchased

(k 1,. . . , 7). The salvage value is estimated to be

$30,000 for years 1 and 2 and $20,000 for years 3 through 7. At i  10% per year, determine the economic service life and equivalent annual worth of the sifter using

(a) tabulated factors, and

(b) a spreadsheet.