In this subsection, “operating ratio” means the relationship of common carrier expenses to common carrier operating revenues. In considering proper revenue under subsection (b)(3) of this section, the Commission shall determine a fair and equitable operating ratio. In setting a just and reasonable rate for common carriers, and classifications, regulations, and practices relating to common carriers, the Commission shall consider, among other factors: the inherent advantages of transportation by common carriers; the need, in the public interest, of adequate and efficient transportation services by common carriers at the lowest cost consistent with furnishing these services; and the need of revenues sufficient to enable common carriers to provide these services under honest, economical, and efficient management.