The employer may enter into a collective bargaining agreement to pay a different employer contribution rate and a different employee contribution rate, provided all of the following conditions are met:

the terms of a collective bargaining agreement that is in effect on January 1, 2014, would be impaired by this subdivision, this subdivision shall not apply to the employer and participants subject to that contract until the expiration of that contract. A renewal, amendment, or any other extension of that contract shall be subject to the requirements of this subdivision.

system and shall remain in effect for at least one plan year. However, the employee contribution rate and the employer contribution rate as determined under the collective bargaining agreement may become effective as of the first day of the plan year in which notice is given if it is so provided in the collective bargaining agreement and if a lump-sum contribution is made to the plan equal to the additional employee and employer contributions, if any, that would have been required if the contribution rates had been in effect on the first day of the plan year. Interest shall be credited at the minimum interest rate with respect to the lump-sum contribution commencing with the first month after the contribution is made.