Refer to the table above. The marginal product of workers falls below zero when the ________ worker is hired

The free-rider problem exists for goods that are ________

A) excludable B) rival C) free D) non-excludable

It is appropriate to use the supply-and-demand model if, in a market,

A) everyone is a price taker with full information about the price and quality of the good. B) firms sell identical products. C) costs of trading are low. D) All of the above.