1. Where an agreement relative to a sabbatical with deferred salary between a person and his employer becomes null, the pensionable salary, credited service and contributions in respect of the years or parts of a year for which the person had agreed to receive only part of his salary shall be determined, for the purposes of the retirement plan to which he contributes, as follows:(1) the pensionable salary shall be the salary paid to the person;
(2) part of the year of service shall be credited in the proportion that the salary paid to the person bears to the salary that would have been paid to him if he had not agreed to receive only part of it;
(3) the contributions recognized shall be the contributions made by the person and any contributions from which he was exempt.