First, if you want to go to the bank to buy foreign exchange, it is at the bank's selling price (higher price); If you want to sell foreign exchange to a bank, it is calculated at the purchase price (low price). Second, if you take cash in Hong Kong dollars to the bank counter, it is according to the purchase price of cash; If you are given foreign exchange in Hong Kong dollars and you don't have cash in Hong Kong dollars, that's the buying price of cash.