A. In determining the eligibility for retirement of an employee, a plan may provide that (a) the period during which such employee was employed by a predecessor bank, and by a bank, savings bank or national bank toward which such predecessor bank stands in the relation of a successor bank; and (b) the period during which such employee was employed by a subsidiary, shall be included in the period of such employee's employment in such bank.
B. In determining the eligibility for retirement of an employee, a plan may provide that a period during which such employee was employed by an employer other than the bank, a predecessor bank, or a subsidiary, shall be included in the period of such employee's employment in such bank.