What is the most economical diameter of a pipeline that is required to transport crude oil $(\mu=$ $30 \mathrm{cP}, \mathrm{SG}=0.95)$ at a rate of 1 million bbl/day using ANSI 1500\# pipe if the cost of energy is $\$ 0.05 / \mathrm{kWh}$ (in 1980 dollars), the economic lifetime of the pipeline is 40 years, and the pumps are $50 %$ efficient.