Supplementary information:
Vending machine (VEM) is a machine that can automatically pay for goods according to the money invested. Vending machine is a common equipment for commercial automation, which is not limited by time and place, and can save manpower and facilitate transactions. It is a brand-new form of commercial retail, also known as 24-hour mini-supermarket. Common vending machines are divided into four types: beverage vending machines, food vending machines, comprehensive vending machines and cosmetics vending machines.