Exchange creates value by moving goods from parties who value the goods less to parties who value the goods more. Both b and c 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.
A nation with cheap, efficient communications is likely to be richer, ceteris paribus, because transaction costs will be lower and trade greater. When private ownership of a resource is clearly defined and enforced, the private owner has a strong incentive to consider the wishes of others when deciding how to employ the resource. Private ownership undermines the conservation of resources. With private ownership, owners are held accountable for using their resources in a manner that harms the resources of others. Private ownership encourages people to act selfishly toward others.