A metal plating company is considering four different methods for recovering by-product heavy metals from a manufacturing site’s liquid waste. The investment costs and annual net incomes associated with each method have been estimated. All methods have an 8-year life; the MARR is 11% per year; and an AW-based ROR analysis is required. (a) If the methods are independent (because they can be implemented at different plants), which ones are acceptable? (b) If the methods are mutually exclusive, determine which one should be selected.
(a) A vs DN: 0 = -30,000(A/P,i*,8) + 4000 + 1000(A/F,i*,8)
Solve for i* by trial and error or spreadsheet
i* = 2.1% (spreadsheet)
Method A is not acceptable
B vs DN: 0 = - 36,000(A/P,i*,8) + 5000 + 2000(A/F,i*,8)
i* = 3.4%
Method B is not acceptable
C vs DN: 0 = - 41,000(A/P,i*,8) + 8000 + 500(A/F,i*,8)
i* = 11.3%
Method C is acceptable
D vs DN: 0 = - 53,000(A/P,i*,8) + 10,500 - 2000(A/F,i*,8)
i* = 11.1%
Method D is acceptable
(b) Revenue alternatives; compare to DN initially
A vs DN: 0 = -30,000(A/P,i*,8) + 4000 + 1000(A/F,i*,8)
Solve for i* by trial and error or spreadsheet
i* = 2.1% (spreadsheet)
Eliminate A; retain DN
B vs DN: 0 = - 36,000(A/P,i*,8) + 5000 + 2000(A/F,i*,8)
i* = 3.4%
Eliminate B; retain DN
C vs DN: 0 = - 41,000(A/P,i*,8) + 8000 + 500(A/F,i*,8)
i* = 11.3%
Eliminate DN; retain C
D vs DN: 0 = - 53,000(A/P,i*,8) + 10,500 - 2000(A/F,i*,8)
i* = 11.1%
Eliminate DN; retain D
D vs C: 0 = - 12,000(A/P,?i*,8) + 2,500 - 2500(A/F,?i*,8)
?i* = 10.4%
Eliminate D
Select method C
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