Jill Has Been Negotiating the Purchase of a Speedboat with Sandi

Jill has been negotiating the purchase of a speedboat with Sandi for the last two weeks. Two days ago, she emailed Sandi, saying "I won't go any higher than $8,000 and that includes the trailer. Take it or leave it, but that's my final offer." Sandi sent an email the same day that said "I will accept $8,000, but not including the trailer." There is a contract between Jill and Sandi.