146.89. The value of the benefits of the members and beneficiaries affected by the withdrawal of an employer or the termination of a plan shall be determined at either of the following dates, using the assumptions referred to in section 61 that are applicable at that date:
(1) the date the member ceased to be an active member, if the benefits whose value is being determined are those accrued to a member whose active membership ended before the date of the withdrawal or termination and who, at that date, had already opted, within the time limit set out in subparagraph 1 of the second paragraph of section 99, for the payment of his or her benefits under the plan or still had time to exercise such an option, or those accrued to a beneficiary whose benefits under the plan derive from the service credited to such a member; or
(2) the date of the withdrawal or termination, if the benefits whose value is being determined are those accrued to any other member or beneficiary affected by the withdrawal or termination, including any member or beneficiary whose pension is not in payment on that date.
The benefits accrued to the members and the beneficiaries referred to in subparagraph 1 of the first paragraph bear interest from the date their value is determined to the date of the withdrawal or termination, at the rate used for the purposes of the determination.