The following money must be paid to the board, which shall credit the payments to the pension trust fund:
(1) all contributions by the various counties as required by this chapter;
(2) all contributions by members as required by this chapter;
(3) all interest on and increase of the investments and money under this chapter; and
(4) any supplemental appropriation or revenue from a source or sources approved by the legislature or money received directly from the federal government for funding of law enforcement retirement systems.