Marsh has a prize horse named Arabian Knight. Marsh is in need of working capital. She borrows $50,000 from Mendez, who takes possession of Arabian Knight as security for the loan. No written agreement is signed. Discuss whether, in the absence of a written agreement, Mendez has a security interest in Arabian Knight. If Mendez does have a security interest, is it a perfected security interest? Explain. (See Perfection of a Security Interest.)