A letter to the contact between customers and companies, which need to ask for details about how to use such kind, quality, price discounts, etc. may be provided by the company itself or send a detailed catalog yet. When the company received a letter of inquiry, I will reply immediately called Letter of Inquiry. To show that the company's focus on its clients and ask a person who is interested. Therefore, it is likely to be remembered. Sales of goods than other types of advertising. But the inquiry may not ask about the details of the product or service. But cooperation in answering questions not related to trading, such