In order to reimburse the General Fund for the costs incurred by the Department of Property and Supplies¹ in purchasing equipment, materials, and supplies for departments, boards, and commissions, as purchasing agency, and for space occupied in the Capitol buildings and water, light, heat, power, telephone and other services utilized and consumed by the departments, boards, and commissions, whose expenses are wholly or mainly paid out of funds other than the General Fund of the State Treasury, such departments, boards, or commissions, to which special operating funds are appropriated for this purpose, shall be billed at least quarterly by the Department of Property and Supplies, upon a cost basis, at such amounts as the Department of Property and Supplies, with the approval of the Executive Board, shall determine. Amounts payable hereunder for reimbursing the General Fund for the above costs shall be paid out of such special operating funds in the State Treasury to the Department of Property and Supplies, and shall be by it paid into the General Fund of the State Treasury through the Department of Revenue.