(a) The maximum allowable rate of return for any exchange carrier's earnings on any access service category shall be determined by adding a fixed increment of four-tenths of one percent of the exchange carrier prescribed rate of return.

(b) The maximum allowable rate of return for any exchange carrier's overall interstate earnings for all access service categories shall be determined by adding a fixed increment of one-quarter of one percent to the exchange carrier prescribed rate of return.

(c) The maximum allowable rate of return for rates filed by local exchange carrier subject to § 61.50 of this chapter, shall be determined by adding a fixed increment of one and one-half percent to the carriers prescribed rate of return.