When economists use the term ceteris paribus, they indicate that the causal relationship between two economic variables cannot be determined. Your opportunity cost of attending a football game is the subjective value of the hardship if your team loses. Exchange permits trading partners to gain from a larger total output as the result of specialization in those areas where they have a comparative advantage. Exchange makes it possible for trading partners to produce more goods through division of labor and adoption of mass production methods. Both a and b are true.
Middlemen add to the expenses of buyers without providing a benefit to sellers.
Our economy would work just as well without middlemen since they do not expand the availability of physical goods. Middlemen reduce the number of transactions since they increase the buyer's price and reduce the seller's net receipts. Middlemen create value by arranging trades and providing information to buyers and sellers. All of the above are correct. A private owner of a resource has a strong incentive to conserve the resource for the future, particularly if it is expected to increase in value.