(a) When jurisdiction shall have been obtained by the Family Division in the case of any child, such jurisdiction may be retained by the Division until he becomes 19 years of age, unless he is discharged prior thereto by the court. This section does not affect the jurisdiction of other divisions of this court or other courts over offenses committed by the child after he reaches the age of 18 years.
(b) If a child already under the jurisdiction of the Family Division is convicted in the Superior Court or District Court of a crime committed after the age of 18, the conviction shall terminate the jurisdiction of the Family Division.
(c) If a child is transferred to another court, and the child is convicted in that court for a crime pursuant to the transfer, the conviction shall terminate the jurisdiction of the Family Division. For any crimes after such conviction, the child shall be considered an adult for the purpose of determining jurisdiction.