I still remember when I was a child, when my parents told me to go to the store to get coins to pay at the stationery store, my hazy memory still couldn't figure out why the coins I took out could be exchanged for the mechanical pencils I wanted. Tong Yan Tongyu's head, the immediate intuition is: "Why can't I take a used automatic pen and exchange it with the boss for a new one?"
From the perspective of the contract, if the store owner is willing to exchange your old automatic pen with a new one in his store, it is of course in line industry email list with the agreement in the contract, but in reality, such a situation is almost impossible. It can't happen, because the boss will demand the value represented in currency as the price to sell the automatic pen.
Then, the value represented by the currency, who ordered it? And how is the price determined? Before discussing this topic, let's talk about "What is Buying and Selling - Trading?" First look at Wikipedia's definition of buying and selling: "exchange one's own goods or services with others in exchange for others' goods or services ."