In: Economics
8. A bridge will cost (in the present) $280 million to build, will
be completed by next year, and will start producing the benefits
next year, $8 million per year. It will cost $1 million a year to
maintain (starting next year, too). It is expected that the bridge
will last for long time. The market interest rate is 5%.
Approximate (with the formula for a perpetuity) the present value
of the bridge project (including the cost of construction,
benefits, and the cost of maintenance).
9. Find out at what interest rate this bridge would be worth
building. The answer should be, “The bridge is worth building if
interest rate is NO MORE THAN ________.”
Initial cost = 280m
Annual benefit = 8m
Annual cost = 1m
Net annual benefit = 8m - 1m = 7m
i = 5%
Present value of net benefits = 7m / 0.05 = 140m
NPV = -280m +140m = -140m
9. For bridge to be worth building 280m = 7m/i
i = 7m / 280m = 0.025 = 2.5%
The bridge is worth building if interest rate is NO MORE THAN 2.5%.”