Horne executed a $100,000 note in favor of R. C. Clark. On the back of the instrument was a restriction stating that the note could not be transferred, pledged, or otherwise assigned without Horne’s written consent. As part of the same transaction between Horne and Clark, Horne gave Clark a separate letter authorizing Clark to pledge the note as collateral for a loan of $50,000 that Clark intended to secure from First State Bank. Clark did secure the loan and pledged the note, which was accompanied by Horne’s letter authorizing Clark to use the note as collateral. First State contacted Horne and verified the agreement between Horne and Clark as to using the note as collateral. Clark defaulted on the loan. When First State later attempted to collect on the note, Horne refused to pay, arguing that the note was not negotiable as it could not be transferred without obtaining Horne’s written consent. Is the instrument negotiable? Explain.