Subject to the requirements set forth in subsection (b) of this section, an issuer of a debenture purchased by the Federal Financing Bank and guaranteed by the Administration under this chapter may, at the election of the borrower (in the case of a loan under section
697 of this title) or the issuer (in the case of a small business investment company) and with the approval of the Administration, prepay such debenture in accordance with the provisions of this section.