The graph illustrates the market for pulp and paper with no government intervention.

When the mills produce pulp and paper, they also create waste, which they dump into a nearby river.

The marginal external cost of the dumped waste is equal to the marginal private cost of producing pulp and paper $($that is$,$ the marginal sociallcost of producing the pulp and paper is double the marginal private cost.$)$

What quantity of pulp and paper is produced if no one owns the river? What is the efficient quantity?

If no one owns the river, the quantity of pulp and paper produced is tonnes a week.

The efficient quantity of pulp and paper is tonnes a

Price $($dollars per tonne$)$ week.