The board may combine the assets of the State Employee and Teacher Retirement Program with the assets of other retirement programs of the retirement system for investment purposes. The assets of the State Employee and Teacher Retirement Program may not be combined with the assets of another retirement program for benefit purposes or for administrative expenses. All of the assets of the retirement system must be credited according to the purpose for which they are held among the several funds created by this section, namely:
1. Members' Contribution Fund. The Members' Contribution Fund; and
2. Retirement Allowance Fund. The Retirement Allowance Fund.
3. Expense Fund.
4. Survivors' Benefit Fund.
5. State Retiree Health Insurance Fund.
6. State Retired Teachers' Health Insurance Fund.
7. Disability Retirement Benefit Fund.