At the end you should sign off with "sincerely yours" or any other related salutation. If you are applying for a particular job then you need to create letter of intent that contains the following. First of all mention your name, address and contact number.
Buyer accepts offer and signs it, where offer acceptance is binding depends of the legal jurisdiction. For example English and common law differs slightly from American uniform commercial law on matters of offer acceptance and when performance becomes binding on an offer. The seller can also reply with a pro forma invoice. In fact a pro forma invoice can serve as quote and offer, becoming a more or less binding purchase order upon buyer acceptance and signing. Pro formas are used more in smaller FCL trades, and not in larger bulk trades.