R&A Concrete Contractors, Inc., executed a promissory note that identifies both R&A Concrete and Grover Roberts as its makers. On the reverse side of the note, the following appears: ‘‘X John Ament Sec. & Treas.'' National Bank of Georgia, the payee, now sues both R&A Concrete and Ament on the note. What rights does National Bank have against R&A and Ament?