(a) Direct testimony to rebut testimony offered during the time period specified in the notice of hearing may be submitted pursuant to these regulations within fifteen days after the conclusion of the prehearing conference unless the presiding officer otherwise specifies in the prehearing order.

(b) If the prehearing order presents issues not included in the notice of the hearing published pursuant to §18.74:

(1) Any person interested in participating at the hearing on such issues presented shall notify the Director by certified mail of an intent to participate not later than ten days after publication of the prehearing order. Such person may present direct testimony or cross-examine witnesses only on such issues presented unless he previously notified the Director pursuant to §18.75; and

(2) Additional written direct testimony concerning such issues may be submitted within the time provided in the prehearing order. Such direct testimony will comply with the requirements of §18.77.