(a) Any trooper first class of the Uniform Division of the Department of Public Safety shall be eligible for promotion to the rank of corporal, provided he has served a period of 12 months in the Georgia State Patrol including the period of probation.
(b) Any noncommissioned or commissioned officer shall be eligible for promotion to a higher rank, provided he has served at least one year in the preceding rank.
(c) Promotions to ranks of corporal through lieutenant shall be made in accordance with the Georgia State Patrol Promotion System.