(a) A party may serve on the department an answer, or responsive pleading, signed by the party or the party's attorney. The answer or responsive pleading shall specify which allegations are admitted, which allegations are denied and which allegations a party has insufficient information upon which to form an opinion.

(b) The answer or responsive pleading shall be served no later than three days before the initial hearing date.

(c) An answer or responsive pleading is required if there are affirmative defenses.