What is on the horizontal axis when we draw a total product curve?

For a good whose production creates a pollution, when marginal social cost equals marginal social benefit, then

I there is no pollution. II resources are utilized efficiently. A) I only B) II only C) neither I nor II D) both I and II

If a marginal cost pricing rule is imposed on the natural monopoly in the figure above, then the firm will

A) incur an economic loss. B) make zero economic profit, that is, its owners make a normal profit. C) make an economic profit of $4 million. D) make an economic profit of $16 million.