Final answer:
The most economical path for the transmission line from the power station to the factory is to run the power lines overland for a cost of $6,000.
Step-by-step explanation:
To find the most economical path for the transmission line from the power station to the factory, we need to compare the costs of running power lines overland and underwater. Since the factory is downstream on the other side of the river, we can assume that the most direct path is underwater. Let's calculate the cost of running the power lines overland and underwater:
Overland path: 1 mile * $6 per foot = $6,000
Underwater path: 6 miles * $8 per foot = $48,000
Based on the calculations, the most economical path for the transmission line would be the overland path, which costs $6,000.