This is determined by the national exchange rate policy and the bank's own cost. The foreign exchange trading center will set the middle price of the day. On the basis of this middle price, banks will set their own middle price and set their own buying and selling prices within the scope stipulated by national policies. At the same time, banks should trade in foreign exchange trading centers, hedge their transactions with customers in the foreign exchange trading market, or hedge the price difference. In the final analysis, they must control the position of foreign exchange settlement and sale within the quota allowed by the state. The position of foreign exchange settlement and sale refers to the difference between customers and buying and selling foreign exchange in the market, which must be within the quota given by the state. Therefore, the operating cost of banks in the market is very important. It specifies its own exchange rate according to the price it gets. In short, I don't know if you can understand.