56. In this Division, unless the context indicates otherwise,(a) “special deficit” means the amount by which the liabilities of a plan calculated in accordance with section 59 exceed its assets calculated in accordance with section 60;
(b) “special balance” means on the date of a plan’s valuation, the sum of the balances of all experience deficiencies, or of all parts of such deficiencies, previously determined and the amortization period of which was not to exceed 5 years;
(c) “final pay plan” means unit benefit plan in which the retirement pension is calculated according to the salary of a determined period in the final years of service, and the number of credited years of service;
(d) “average best earnings plan” means unit benefit plan in which the retirement pension is calculated according to the highest salary earned during a determined period in the career and to the number of credited years of service.