When evaluating a new public park, which of the following best describes the Marginal Social Benefit (MSB) associated with its creation?

Marginal Social Benefit is the extra benefit society gets from adding one more unit of the park, and it includes not only the people who use the park directly but also everyone who enjoys cleaner air, lower crime, or a nicer neighborhood. It is the private benefit to visitors plus any positive spill‑over effects that spill into the community. So the MSB is higher than the private benefit alone because it adds the value of the positive externalities. For example, if a new park makes nearby houses more attractive and raises local property values, that increase is part of the MSB. Thus, the MSB is the sum of all those incremental benefits to society from the park’s creation.