Two possible routes for a power line are under study. In both cases the power line will last 15 years, have no salvage value, have annual property taxes of 2% of ?rst cost, and have a yearly power loss of $500/km.

	Around the lake	Under the lake
Length	15 km	5 km
First cost	$9000/km	$25,000/km
Maintenance	$200/km/yr	$300/km/yr

If 6% interest is used, should the power line be routed around the lake or under the lake?