(3) the share of the fees received by each lawyer or law firm or the basis on which the division is carried out if the apportionment is based on the share of the service provided. The consent of a client or potential client to the transfer to or to the association of another lawyer prior to such a transfer or grouping, but without knowledge of the information referred to in paragraph (f) (2), does not constitute sufficient confirmation of the client within the meaning of this Rule. The expelling or associative lawyer or any other lawyer appointed to assist another lawyer in the representation has the main obligation to ensure full disclosure and compliance with this rule. (d) A lawyer may not enter into, charge or withdraw a contract for fees for professional employment obtained in violation of Rules 7.03 (a), (b) or (c). A lawyer`s referral agreement allows a lawyer from another law firm to cooperate with a case for a fee or to take over it in full. . . .