(a) The board of commissioners may appoint all necessary agents for carrying on the work and may fix their pay and shall pay a reasonable fee for legal services in organizing the district and for circulating petitions.
(b) The board may sell all unnecessary material and implements that may be on hand and which may not be necessary for the completion of the improvement under way, or which may have been completed, and may in general make all contracts in the prosecution of the work as may best subserve the public interest.