Well, let me tell you my understanding. I am also a junior high school student.

A credit transaction is a contract in which one party agrees to give money or resources to the other party for a certain amount of time. If you give something to the other party after the time, but it cannot exceed the time limit of the credit sales contract, you will have to compensate for breach of contract

Runrun and Amati have a lot of ore, and if the price increases, Matti can sell a lot and there will be enough to buy the queen. If the price is low, it will be very expensive. If someone buys the ore at this time, the price will increase. If someone sells the ore at this time, the price will decrease, so Runrun He and the queen sold a lot, causing Amati to lose money

That's it

The ore was exchanged for 250 pieces of wheat because someone was exchanging wheat for the ore, so Runrun gave Neland a pack. What Maizi brought back was the ore. I can’t understand the price tag, but if someone is selling the ore, put the price tag on it. If someone is buying the ore, put the price tag on it.