AW(Benefits– O&M, I) =$550,000 –$180,000 =$370,000
AW(Benefits– O&M, II) =$540,000 –$125,000 =$415,000
AW(Costs, I) =$1,250,000(A/P, 3%, 28) –$11,000(A/F, 3%, 28)
=$1,250,000(0.0533) –$11,000(0.0233)
=$66,368.70
AW(Costs, II) =$1,050,000(A/P, 3%, 28) –$9800(A/F, 3%, 28)
=$1,050,000(0.0533) –$9800(0.0233)
=$55,736.66
Rank order: DN II I
B/CModified (II) =$415,000/$55,736.66
=7.45
B–C(II) > 1.0; therefore, Alternative II is acceptable.
B
CModified(I–II) = $(10,000– 55,000)/[$200,000(A/P, 3%, 28)– $1,200(A/F, 3%,
28)] = –$45,000/[$200,000(0.0533)– $1,200(0.0233)]
= –4.23
B
C(I–II) < 1.0; therefore, the increment required for Alternative I is not
acceptable.
Select Alternative II.
For flood control purposes, the government is considering three undeveloped sites for a
water detention area. The estimated costs associated with each alternative are given
below. Use the conventional B–C ratio method, with AW as the equivalent–worth
measure, to determine which alternative should be selected at an interest rate of 6% per
year. Assume the site will be used for 17 years before being developed for other purposes.
Site A Site B Site C
Initial cost, $ $1,350,000 $1,250,000 $1,500,000
Annual maintenance, $/yr $320,000 $300,000 $345,000
Annual benefits, $/yr $1,540,000 $1,500,000 $1,595,000
Annual disbenefits, $/yr $530,000 $500,000 $560,000