(a) Within 20 days of receipt of the complaint or UAC, but no later than 5 days before the date of the hearing, whichever is shorter, the respondent shall serve upon the commission an answer, signed by the respondent or the respondent's attorney.

(b) The respondent shall specify in the answer which allegations are admitted, which allegations are denied and which allegations the respondent lacks sufficient information upon which to form an opinion as to the allegation.

(c) The respondent's answer may contain affirmative defenses; in which event the answer shall contain a statement of any facts which constitute the grounds of the affirmative defense.

(d) If the complaint or UAC is so vague or ambiguous that respondent cannot reasonably be required to frame an answer, the respondent may move for a more definite statement within 10 days of receipt of service. If the motion is denied, the respondent shall answer within 10 days of receipt of notice that the motion is denied. If the motion is granted, the commission shall serve an amended complaint or UAC within 10 days of receipt of notice that the motion is granted, and the respondent shall answer pursuant to subdivisions (a) through (c) of this section.

(e) The failure to file an answer or the failure by the respondent to appear on the return date or at the hearing shall constitute a default and a waiver of hearing upon proof of service of a notice of hearing and a complaint or a UAC.