(a) The Commissioner of Labor and the union or association of employees which has filed or submitted the device shall, within 30 days after receipt of the petition, file their answers with the board or move with respect to the petition.

(b) The respondents shall each serve personally or by mail one copy of the answer upon petitioner, or the attorney or authorized representative of record, and shall file the original with the board with proof of such service.

(c) Each answer shall be so drawn as to advise the petitioner and the board of the nature of the defense in reasonable detail. It shall contain a specific admission, denial or explanation of each of the material facts alleged in the petition. Such a denial may be upon information and belief or a denial of knowledge or information sufficient to form a belief as to the truth of the allegation. The answer must also contain a statement of any facts upon which the respondent relies for an affirmative defense.