project, Texas secured a federal grant for $3 million that paid for 200 mobile cameras in
strategic high-traffic areas. If the 200 cameras are considered to be equivalent to
20 border patrol agents, each with an annual salary of $75,000, what is the rate of return
over a 3-year project period?
Problem 6.14
The University of California at San Diego is considering a plan to build a 8- megawatt
cogeneration plant to provide for part of its power needs. The cost of the plant is
expected to be $41 million. The university consumes 55,000 megawatt-hours per year at
a cost of $120 per megawatt-hour. (a) If the university will be able to produce power at
half the cost that it now pays, what rate of return will it make on its investment for an
expected power plant life of 30 years? (b) If, in addition, the university can sell an
average of 12,000 megawatt-hours per year back to the utility at $90 per megawatt-hour,
what rate of return will it make?
Problem 6.15
The Camino Real Landfill was required to install a plastic liner to prevent leachate from
migrating into the groundwater. The fill area was 50,000 m2 and the installed liner cost
was $8 per square meter. In order to recover the investment, the owner charged $10 for
pick-up loads, $25 for dump truck loads, and $70 for compactor-truck loads. The annual
distribution is 2400 pick-up loads, 600 dump truck loads, and 1200 compactor-truck
loads. What rate of return will the landfill owner make on the investment if the fill area
is adequate for 4 years?
Problem 6.16
U.S Census Bureau statistics show that the annual earnings for a person with a high-
school diploma are $35,220 versus $57,925 for someone with a bachelor’s degree. If the
cost of attending college is assumed to be $30,000 per year for four years and the
foregone earnings during those years is assumed to be $35,220 per year, what rate of
return does earning a bachelor’s degree represent? Assume a 35-year study period.
Problem 6.17
Rubber sidewalks made from ground-up tires are said to be environmentally friendly and
easier on peoples’ knees. Rubbersidewalks, Inc. of Gardena, CA, manufactures the small
rubberized squares that are installed where tree roots, freezing weather, and snow
removal require sidewalk replacement or major repairs every three years. The District of
Columbia spent $60,000 for a rubber sidewalk to replace broken concrete in a residential
neighborhood lined with towering willow oaks. If a concrete sidewalk costs $28,000 and
lasts only 3 years versus a 9-year life for the rubber sidewalks, what rate of return does
this represent?