29.1. For the purposes of the application of section 85.5 of the Act, the agreement between the employee and his employer becomes void by reason of any of the following circumstances:
(1) the time worked is less than 40% of the regular time of a full-time employee holding such a position;
(2) the employee voluntarily ceases to participate in this plan during the first year of his participation in the agreement;
(3) an employee eligible for a pension does not cease participating in this plan on the expiry of the period agreed upon;
(4) (paragraph revoked).