资料题：In the last sentence, the word“they" refers to（　）。

Prices determine how resources are to be used.They are also the means by which productsand services that are in limited supply are rationed among buyers.The price system of the UnitedStates is a very complex network composed of the prices of all the products bought and sold in the economy as well as those of a myriad of services, including labor, professions, transportation,and public-utility services.The interrelationship of all these prices makes the"system" of prices.The price of any particular product or service is linked to a broad, complicated system of prices in which everything seems to depend more or less on everything else.If one were to ask a group of randomly selected individuals to define" price" , many would reply that price is an amount of money paid by the buyer to the seller of a product or service, or,in other words, that price is the money value of a product or service as agreed upon in markettransaction.This definition is, of course, valid as far as it goes.For a complete understanding of a price in any particular transaction, much more than the money involved must be known.Both the buyer and seller should be familiar with not only the money amount, but with the amount and quality of the product or service to be exchanged, the time and place at which the exchange will take place and payment will be made, the form of money to be used, the credit terms and discounts that apply to the transaction, guarantees on the product or service, delivery terms, return privilege, and other factors.In other words, both sides should be fully aware of all factors that compose the total"package" being exchanged for the asked-for amount of money in order that they may evaluate a given price.