A welding machine is an example of a factor of production if it is being used to produce automobiles

The long-run supply curve for a perfectly competitive, constant-cost industry

A) is found by adding up the marginal cost curves for all firms in the industry. B) is horizontal. C) is upward-sloping. D) is downward-sloping.

It is assumed that the marginal benefit of air cleanliness falls with the degree of cleanliness since

A) the marginal cost of air cleanliness increases. B) air cleanliness is a public good and not a private good. C) the marginal utility of air cleanliness falls with the degree of cleanliness. D) the generation of pollution should be considered an externality.