(1) When a petition for unit determination proposes a unit which contains both professional and nonprofessional employees, and the unit is found to be appropriate by this division, an election will be conducted among the professional employees to determine whether or not they wish to be included in the proposed unit.

(a) If a majority of the professional employees do not desire to be included in the proposed unit, they shall be excluded from the unit.

(b) If a majority of the professional employees desire to be included in the unit they shall be included in the unit.

(2) Notice of the special election shall be posted by the employer no less than five days prior to the election.