Concept:A written request made by a buyer to a seller for product details before making a purchase.Explanation:A formal letter written to a dealer to ask for details about items for sale is best described as an inquiry.It is used to request information such as prices, quality, availability, or conditions of sale.An inquiry is made before the buyer places an order, and it often leads to a quotation from the seller.An invoice and an order come after the decision to buy, while a quotation is the seller's response.Answer:A. an inquiry