The Board of Trustees of the Public Employees’ Retirement System, as created by Sections 25-11-1 through 25-11-139, shall act as custodian of this Disability and Relief Fund for members of the Mississippi Highway Safety Patrol; shall receive to the credit of such fund all appropriations and other funds available as an employer’s contribution thereto from any source whatsoever; and the Highway Safety Patrol shall each month deduct from the salary of each member, as defined in Section 25-13-3, five percent (5%) thereof, and shall pay the amount so deducted to the Board of Trustees of the Public Employees’ Retirement System to be credited to the Disability and Relief Fund for the members of the Mississippi Highway Safety Patrol. Provided, however, that the said board of trustees may, biennially, following March 18, 1977, vary the percentage of employee contribution on the basis of the liabilities of the retirement system for the various allowances and benefits as shown by actuarial valuation. From the funds credited to this account, the Board of Trustees of the Public Employees’ Retirement System shall pay retirements, disability benefits, survivors benefits, expenses and shall refund contributions as provided in this chapter. The said “Disability and Relief Fund for the Mississippi Highway Safety Patrol” shall be maintained as a separate fund, separate from all other funds held by the Board of Trustees of the Public Employees’ Retirement System of Mississippi and shall be used only for the payment of benefits provided for by this chapter, or amendments thereto.