(a) The retirement system shall immediately deposit all money received by the system with a depository designated under Section 855.109.
(b) When securities of the retirement system are received, the system shall deposit the securities in trust with a depository designated under Section 855.109. The depository shall provide adequate safe deposit facilities for the preservation of the securities.
(c) All assets of the retirement system shall be credited, according to the purpose for which they are held, to one of the following funds:
(1) benefit accumulation fund;
(2) interest fund;
(3) endowment fund;
(4) expense fund;
(5) supplemental disability benefits fund; or
(6) supplemental death benefits fund.