Final answer:
Among the given options, Nicole paying her college tuition is most likely to emit a positive externality because education typically leads to significant social benefits, such as an educated workforce and higher economic growth, which are beneficial to society at large.
Step-by-step explanation:
The expenditure most likely to emit a positive externality among the options provided is Nicole paying her college tuition. Investing in education typically produces significant social benefits beyond the private gains received by the individual student.
Such benefits include a more educated workforce, which can lead to greater innovation, improved productivity, and potentially higher economic growth. The positive externalities in this case might manifest as increased knowledge shared with peers and the spread of skills within the community.
On the other hand, when a firm like State Farm Insurance buys a new computer, Shell Oil leases a new oil field, or United Van Lines buys a new truck, the external benefits to society are relatively limited compared to the private benefits the specific company would receive. While these investments can contribute to more efficient business operations and possibly lower prices for consumers, they do not have the same broad societal impact as an individual's educational attainment.