A labor organization or individual that purports to represent a substantial number of employees whom a petition affects and an employer may submit to the Mediation Service a petition for permission to enter into a consent election agreement leading to a determination by the Mediation Service of the facts ascertained after the consent election. A petition shall be in the form that the Mediation Service requires. Whenever a petition is submitted in accordance with subsections (a) and (b) of this section, the Mediation Service shall set a period during which a labor organization may submit an objection to the petition. The Mediation Service shall set a period that: is sufficient to inform interested persons about the nature and purpose of the petition; and does not expire until at least 1 week after the date on which the Mediation Service causes notice of the petition to be posted. The Mediation Service shall cause notice of a petition to be posted, at each place of employment that the petition affects, for the period set under subsection (c) of this section. The notice shall state that a labor organization may object to the petition within the period set under subsection (c) of this section.