If a Monopolist Produces Output in More Than One Plant

If a monopolist produces output in more than one plant, output should be distributed among those plants so that:

A) the total costs of production are the same in each plant
B) the marginal revenue of producing the last unit of output in each plant is the same for all plants
C) the average total cost of producing the last unit of output in each plant is the same for all plants
D) the average revenue of producing the last unit of output in each plant is the same for all plants