(b) Until December 31, 2001, any portion of the Common Line element annual revenue requirement that is attributable to CPE investment or expense or surrogate CPE investment or expense shall be assigned to the Carrier Common Line element or elements.(c) Until December 31, 2001, any portion of the Common Line element annual revenue requirement that is attributable to customer premises wiring included in IOT investment or expense shall be assigned to the Carrier Common Line element or elements.(e) Until December 31, 2001, any portion of the Common Line element revenue requirement that is not assigned to Carrier Common Line elements pursuant to paragraphs (b) and (c) of this section shall be apportioned between End User Common Line and Carrier Common Line pursuant to § 69.502 . Such portion of the Common Line element annual revenue requirement shall be described as the base factor portion for purposes of this subpart.(f) Beginning January 1, 2002, the Common Line element revenue requirement shall be apportioned between End User Common Line and Carrier Common Line pursuant to § 69.502 . The Common Line element annual revenue requirement shall be described as the base factor portion for purposes of this subpart.48 FR 10358, Mar. 11, 1983, as amended at 50 FR 18262, Apr. 30, 1985; 52 FR 21542, June 8, 1987; 52 FR 37314, Oct. 6, 1987; 61 FR 65364, Dec. 12, 1996; 62 FR 31939, June 11, 1997; 66 FR 59733 , Nov. 30, 2001