An Efficient Level of Provision of a Public Good Is

An efficient level of provision of a public good is achieved when

A) the cost of providing an extra unit of the good is equal to the price of the good.
B) the cost of providing an extra unit of the good is equal to the valuation of each consumer of the extra unit.
C) voters are satisfied that an adequate amount of the good is being produced.
D) the cost of providing an extra unit of the good is equal to the sum of the valuations of all consumers for that unit.
E) the valuation of each consumer for the last unit of the good produced is zero.