On July 1 Judy receives an offer by mail from Bob to sell Bob's BMW for $30,000. Bob includes in the letter that the offer will be open until July 15. On July 12, Judy sends a return letter by U.S. Postal Service certified return receipt accepting the offer. For an unexplained reason, Bob does not receive the letter until July 17. On July 16 Bob and Frank agree on a sale of the car for $31,000. Judy wants the car. 1