Suppose that a vaccine is developed for a highly contagious strain of flu.The likelihood that anyone will get this flu decreases as more people receive the vaccine.One of the demand curves in the diagram reflects private benefits and the other reflects social benefits. 
Refer to the figure above.The socially optimal number of vaccines is _______.
Definitions:
Foraging
The act of searching for and exploiting food resources in the wild, often used in the context of animals but also applicable to human gathering activities.
Commensalism
A relationship between two living organisms where one benefits and the other is neither harmed nor benefits significantly.
Parasitism
A biological relationship where one organism, the parasite, lives on or in another organism, the host, causing it harm.
Apex Predator
is a predator at the top of a food chain, with no natural predators of its own, playing a crucial role in maintaining the health and balance of ecosystems.
Q10: Consumers know that some fraction X of
Q16: Suppose Erie Textiles can dispose of
Q24: Suppose Erie Textiles can dispose of
Q38: Hotelling's model has been used to describe
Q48: Emotions like guilt and sympathy:<br>A) are irrelevant
Q52: Demographers predict that the average age of
Q62: Suppose that the salary range for recent
Q68: Professor Plum,who earns $75,000 per year,read in
Q73: This graph shows the marginal costs and
Q79: For a given occupation,jobs with a large