The notice of hearing shall include:
(a) A copy of the charge;
(b) A statement of the time of the hearing which shall be not less than 10 days after service of the notice of hearing, except in extraordinary circumstances. All charges involving a ``refusal to bargain'' allegation and all charges, if sustained, that would require the setting aside of an election, or the conducting of a new election shall be given first priority;
(c) A statement of the place and nature of hearing;
(d) A statement of the legal authority and jurisdiction under which the hearing is to be held;
(e) A reference to the particular section of the policy and rules and regulations of this chapter involved;
(f) A copy of the determination, if any, made causing the invocation of these formal proceedings.