All moneys received from the issuance of bonds shall be used solely to defray the cost of acquiring or improving an electric plant, except that such proceeds may in the discretion of the supervisory body also be used for the payment of the interest on the bonds during the first two (2) years following the date of such bonds. The cost of the electric plant shall include all costs of acquisition, or improvement, including all preliminary expenses described in Section 77-5-423, the cost of acquiring all property, franchises, easements, and rights in the judgment of the supervisory body necessary or convenient therefor, engineering and legal expenses, expenses for estimates of cost and revenues, expenses for plans, specifications and surveys, other expenses incident or necessary to determining the feasibility or practicability of the enterprise, administrative expense, and such other expense as may be incurred in the financing herein authorized, the acquisition or improvement of the electric plant, the placing of such plant in operation, including the creation of a cash working fund, and the performance of the things herein required or permitted in connection therewith.