A factory building is located in an area subject to occasional flooding by a nearby river. You have been
brought in as a consultant to determine whether flood proofing of the building is economically justified.
The alternatives are as follows:
A. Do nothing. Damage in a moderate flood is $10,000 and in a severe flood, $25,000.
B. Alter the factory building at a cost of $15,000 to withstand moderate flooding without damage
and to withstand severe flooding with $10,000 damages.
C. Alter the factory building at a cost of $20,000 to withstand a severe flood without damage.
In any year the probability of flooding is as follows: 0.70, no flooding of the river; 0.20, moderate flooding;
and 0.10, severe flooding. If interest is 15% and a 15-year analysis period is used, what do you
recommend?
Solution:
A.). Expected damages = (10,000 "\\times" 0.20) + (25,000 "\\times" 0.10) = 2,000 + 2,500 = 4,500
Equivalent Annual Cost (EAC) = "\\frac{Expected \\; damages}{NPV}"
NPV = "(1-\\frac{1}{1+0.15^{15} }) \\div 0.15 = \\frac{0.877}{0.15} = 5.85"
Equivalent Annual Cost (EAC) = "\\frac{4,500}{5.85} = 769.23"
B.). Expected damages = (15,000 "\\times" 0.20) + (10,000 "\\times" 0.10) = 3,000 + 1,000 = 4,000
Equivalent Annual Cost (EAC) = "\\frac{Expected \\; damages}{NPV}"
NPV = "(1-\\frac{1}{1+0.15^{15} }) \\div 0.15 = \\frac{0.877}{0.15} = 5.85"
Equivalent Annual Cost (EAC) = "\\frac{4,000}{5.85} = 683.76"
C.). Expected damages = (20,000 "\\times" 0.10) = 2,000
Equivalent Annual Cost (EAC) = "\\frac{Expected \\; damages}{NPV}"
NPV = "(1-\\frac{1}{1+0.15^{15} }) \\div 0.15 = \\frac{0.877}{0.15} = 5.85"
Equivalent Annual Cost (EAC) = "\\frac{2,000}{5.85} = 341.88"
I recommend option C. Alter the factory building at a cost of $20,000 to withstand a severe flood without damage.
This is because option C has the lowest Equivalent Annual Cost.
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