Determine whether each of the following policy interventions is designed to increase supply or decrease demand for a public good or common resource.

a. A city government increases the frequency of street sweeping.

b. London begins charging a toll to all vehicles that drive within the city limits.

c. A gated community passes a bylaw requiring all homeowners to mow their lawns once a week during the summer.

d. The National Park Service increases the cost of a pass to enter the Everglades.