meet the requirements of section 2(a) for a calendar year shall be subject to a civil money penalty of $100 per calendar year for each employee to whom such failure relates. (B) Exceptions No civil money penalty shall be imposed under this paragraph for a failure to meet the requirements under section 2(a)— (i) during a period for which the Secretary determines that the employer subject to liability for the civil money penalty did not know that the failure existed and exercised reasonable diligence to meet the requirements of section 2(a)