Except for the petitioner, all parties shall file with the director within 10 working days after receipt of a copy of the petition from the director, an original and three copies of a response to the petition containing a signed declaration of its truthfulness by an identified representative of the responding party, with proof of service of a copy thereof upon all other parties. The response shall include a specific admission, denial or explanation of each allegation made by the petitioner, a description of the unit claimed to be appropriate by the responding party for the purpose of collective bargaining and a clear and concise statement of any other facts which the responding party claims may affect the processing or disposition of the petition.