(a) To refund the outstanding bonds of the district upon a finding by the board of commissioners that the refunding is in the public interest;
(b) To improve or extend the structures or facilities of the district or to conduct projects of the district; and
(c) To enter into cooperative agreements with the state or federal government, or both, to obtain financial assistance in the form of loans or grants as may be available from the state or federal government, or both (reference to the state or federal government as used in this section shall specifically include any agency thereof).