A general manager wants to know the economic service life for currently owned machines. (a) Find this value at 20% per year if the first cost is $5,000 per machine. (b) Plot the annual worth curve and determine if it is insensitive over some range of n values Year Trade-in value, $ Estimated AOC, $ 0 5000 1 3000 2000 2 1500 2500 3 1000 3000 4 500 3500 UI 0 4000 6 5000