The efficient quantity of a public good produced is achieved where marginal revenue product equals marginal factor cost. Thus option (a) is correct.
A public good refers to a commodity or service that is made available to all members of a society. Typically, these services are administered by governments and paid for collectively through taxation.
The examples of public goods include law enforcement, national defense and the rule of law.
A public good must be non-rivalrous ( means that the goods do not dwindle in supply as more people consume them) and non-excludable (means that the good is available to all citizens).
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