(a) If upon such investigation the rates, tolls, charges, schedules, or joint rates shall be found to be unjust, unreasonable, insufficient, or unjustly discriminatory, or to be preferential or otherwise in violation of any of the provisions of this chapter, the Commission shall have power to determine and by order fix and order to be substituted therefor such rate or rates, charges, or schedules as shall be just and reasonable. If upon such investigation, it shall be found that any regulation, time schedule, act, or service, complained of is unjust, unreasonable, unsafe, inadequate, preferential, unjustly discriminatory, or otherwise in violation of any of the provisions of this chapter, or if it be found that reasonable service is not supplied, the Commission shall have power to determine and substitute therefor such other regulations, time schedule, service, or acts and to make such orders respecting any such changes in such regulations, time schedules, service, or acts as shall be just and reasonable. The Commission shall have power to fix, determine and require such extensions, expansions, or increases in facilities or service as the Commission finds are in the furtherance of the public convenience and necessity, and the terms and conditions upon which the same shall be made: provided, that no hearing shall be had and no order shall be made with respect thereto without notice to the public utility affected thereby, as provided in section 22 of this title.
(b) In exercising its authority to prescribe just and reasonable rates, the Commission shall provide a return of not less than six (6) nor more than eight (8) percent on the net investment in the property prudently acquired for and devoted to the public use, unless the Commission makes a special finding that a different return is imperative, so as to be fair to the consumer interest, and to be fair to the investor interest by providing a return commensurate with returns in other enterprises having corresponding risks, and which will assure confidence in the financial integrity of the enterprise, so as to maintain its credit and to attract capital.