"Generally, employees returning from a break-in-service of 13 weeks or more (26 weeks in the case of an educational institution) may be treated as newly hired. Alternatively, under a 'rule of parity,' an employer may treat a rehired employee who has had a break of at least four weeks as a new employee if the employee's break in service (with no credited hours of service) is longer than the employee's period of service immediately preceding the break in service. But if an employee's break in service is less than 13 weeks (or 26 weeks in the case of an educational institution), and the employee previously qualified for coverage during the then current stability period, he or she is treated, upon rehire or resumption of service, as a continuing employee to whom coverage must be offered by the first day of the following month."