Indicate which of the following activities create a positive externality, a negative externality, or no externality at all:
a. During a live theater performance, an audience member’s cell phone loudly rings.
b. You are given a flu shot.
c. You purchase and drink a soda during a break from class.
d. A college fraternity and sorority clean up trash along a two-mile stretch on the highway.
e. A firm dumps chemical waste into a local water reservoir.
f. The person down the hall in your dorm plays loud music while you are trying to sleep.