In the process of commodity exchange, the symbol of value is usually used as the medium. From the ancient times when universal equivalents were used to the present day when electronic payment is gradually replacing cash in China. The materiality of currency is constantly weakening, and almost only the symbolic "signifier" remains.
    Tong completed a transaction with cash in the store, trying to make the weight and amount of cash spent on the purchase exactly equal to the weight and price of the goods purchased.