(a) Filing and service. If the answer asserts a counterclaim or a setoff, the complainant may file a reply in writing within 20 days after service of the answer on such person. If any reply or amended reply is filed, it shall be served on the respondent.

(b) Contents. The reply shall be confined strictly to the matters alleged in the counterclaim or setoff asserted in the answer. It shall contain a precise statement of the facts which constitute the grounds of defense to the counterclaim or setoff and shall specifically admit, deny, or explain each of the allegations of the answer constituting such counterclaim or setoff, except that, if the complainant is without knowledge, the reply shall state that.

(c) Failure to file. If no reply is filed, the allegations of the answer shall be regarded as denied.