This transaction, if it is between merchants, would fall under the Uniform Commercial Code (UCC), which has been adopted in every state.
Chapter 672 of the Florida Statutes is the chapter that deals with sale of goods. You can read this chapter and its statutes at
http://www.flsenate.gov/statutes/index.cfm?App_mode=Display_Statute&URL=Ch0672/ch0672.htm
UCC section 2-201 (which is FL statute 672.201)states that a transaction for the sale of goods costing at least $500 MUST be in writing or it is not enforceable unless any of the following apply:
(1) there is some writing confirming the sale signed by the person against whom enforcement is sought;
(2) within a reasonable time after the sale a writing confirming the sale is sent or received;
(3) the goods were specially manufactured for the buyer and cannot be sold to anyone else in the sellers course of business;
(4) if the person against whom enforcement is sought admits in court or court documents that sale did occur;
(5) if the goods were accepted and paid for or received and accepted.
Because in your example B accepted and received the goods, his actions fulfill one of the exceptions to the requirement that a sale of $500 or more must be in writing. Therefore, even under the UCC 2-201 statute of frauds requirement, the sale is enforceable by A and B must pay for the goods.
PLEASE NOTE: Responses here are for information/education only, NOT legal advice and do not form attorney-client relationship! Only licensed attorneys you hire in your state can provide legal advice.