After the entry of an Authority order directing payment of backpay, or the entry of a court decree enforcing such order, if it appears to the Regional Director that a controversy exists between the Authority and a Respondent regarding backpay that cannot be resolved without a formal proceeding, the Regional Director may issue and serve on all parties a notice of hearing before an Administrative Law Judge to determine the backpay amount. The notice of hearing shall set forth the specific backpay issues to be resolved. The Respondent shall, within 20 days after the service of a notice of hearing, file an answer in accordance with § 2423.20. After the issuance of a notice of hearing, the procedures provided in subparts B, C, and D of this part shall be followed as applicable.