Explain how each of the following illustrates one of the four principles of interaction.

a. At a college tutoring co-op, students can arrange to provide tutoring in subjects they are good in (like economics) in return for receiving tutoring in subjects they struggle with (like philosophy).

b. The local municipality imposes a law that requires bars and nightclubs near residential areas to keep their noise levels below a certain threshold.

c. To provide better care for low-income patients, the local municipality has decided to close some underutilized neighborhood clinics and shi funds to the main hospital.

d. On Amazon, books of a given title with approximately the same level of wear and tear sell for about the same price.