18(1)If the CAC accepts an application under paragraph 11(2) or 12(2) it must try to help the parties to reach within the appropriate period an agreement as to what the appropriate bargaining unit is.
(2)The appropriate period is—
(a)the period of 20 working days starting with the day after that on which the CAC gives notice of acceptance of the application, or
(b)such longer period (so starting) as the CAC may specify to the parties by notice containing reasons for the extension.