Bidding documents that are not sealed according to the requirements of the bidding documents are invalid.

A supplier is an enterprise or an individual who provides various needed resources to an enterprise and its competitors, including raw materials, equipment, energy and services. Their situation will have a great impact on the marketing activities of enterprises, such as the price change and shortage of raw materials, which will affect the price and delivery time of enterprise products, and then weaken the long-term cooperation and interests between enterprises and customers. Therefore, marketers must have a comprehensive understanding and thorough analysis of suppliers. In business negotiations, suppliers are both rivals and partners.