(k) Upon the death of a retired member on or after January 1, 2015, there shall be paid a death benefit to the person or persons designated by the member or, if not survived by a designated beneficiary, to the deceased retired member's legal representative; provided the retired member has elected, when first eligible, to make, and has continuously made, in advance of the member's death required contributions as determined by the Board of Trustees on a fully contributory basis, through retirement allowance deductions or other methods adopted by the Board of Trustees, to a group death benefit trust fund, the North Carolina Teachers' and State Employees' Benefit Trust, administered by the Board of Trustees separate and apart from the Retirement System's Annuity Savings Fund and Pension Accumulation Fund. Employer and non-employer contributions to the Benefit Trust and earnings on those contributions are irrevocable. The assets of the Benefit Trust are dedicated to providing benefits to members and beneficiaries in accordance with the Plan's benefit terms. The assets of the Benefit Trust are not subject to the claims of creditors of the employees and non-employees making contributions to the Benefit Trust, are not subject to the claims of any creditors of the Benefit Trust's trustees and administrators, and are not subject to the claims of creditors of members and beneficiaries. Benefit Trust assets may be used for reasonable expenses to administer benefits provided by the Fund as approved by the Board of Trustees. The death benefit payable under this subsection shall be a lump-sum payment in the amount of ten thousand dollars ($10,000) upon the completion of 24 months of contributions required under this subsection. Should death occur before the completion of 24 months of contributions required under this subsection, the deceased retired member's designated beneficiary or beneficiaries, or legal representative if not survived by a designated beneficiary, shall be paid the sum of the retired member's contributions required by this subsection plus interest to be determined by the Board of Trustees.