(a) The fee is determined by the use of the Official Medical Fee Schedule as defined in Section 9791.1 of these rules. For services provided on and after January 1, 1994, the conversion factors to be applied to unit values in the schedule are as follows:

(b) For services in the Evaluation and Management Services Section provided on and after April 1, 1999, the conversion factor to be applied to unit values in the schedule is $8.50.

(c) The conversion factor shall be multiplied by the listed unit value (also known as relative value) of the procedure as set forth in the Official Medical Fee Schedule to establish the reasonable maximum fee. A medical provider or a licensed health care facility may be paid a fee in excess of the reasonable maximum fees if the fee is reasonable, accompanied by itemization, and justified by an explanation of extraordinary circumstances related to the unusual nature of the services rendered; however, in no event shall a physician charge in excess of his or her usual fee.