(a) Except where a longer period is expressly provided in this title, the Commissioner shall give written notice of the hearing to all parties not less than 20 days in advance.
(b) If any such hearing is to be held for consideration of rules and regulations of the Commissioner or of other matters which, under subsection (a) of this section, would otherwise require separate notices to more than 30 persons, in lieu of other notice the Commissioner may give notice of the hearing by publication in a newspaper of general circulation in this State, at least once each week during the 4 weeks immediately preceding the week in which the hearing is to be held; except that the Commissioner shall mail such notice to all persons who have requested the same in writing in advance and have paid to the Commissioner the reasonable amount fixed by the Commissioner to cover the cost thereof.