Refer to the graph shown, which shows the demand and supply for a new vaccine against the common cold. Suppose once vaccinated, a person cannot catch a cold or give a cold to someone else. At the competitively determined output level, the marginal social benefit will be: 
Definitions:
Proportion
A statistical measure that refers to the fraction of the total that possesses a certain attribute or characteristic.
Mutually Exclusive
Two events that cannot happen at the same time, meaning the occurrence of one event excludes the occurrence of the other.
Independent Events
Two or more events that have no impact on the likelihood of each other's occurrence.
P(A And B)
The chance of event A occurring together with event B.
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