(1) The number of judges of the separate juvenile court in counties which have established a separate juvenile court shall be:
(a) Two judges in counties having seventy-five thousand inhabitants but less than two hundred thousand inhabitants;
(b) Four judges in counties having at least two hundred thousand inhabitants but less than four hundred thousand inhabitants; and
(c) Six judges in counties having four hundred thousand inhabitants or more.
(2) The senior judge in point of service as a juvenile court judge shall be the presiding judge. The judges shall rotate the office of presiding judge every three years unless the judges agree to another system.