A person authorized to make an anatomical gift under § 4–507 of this subtitle may make an anatomical gift: By a document of gift signed by the person making the gift; or By an oral communication that is electronically recorded or is contemporaneously reduced to a record and signed by the individual receiving the oral communication. Subject to subsection (c) of this section, an anatomical gift by a person authorized under § 4–507 of this subtitle may be amended or revoked orally or in a record by a reasonably available member of a prior class. If more than one member of a prior class is reasonably available, the gift made by a person authorized under § 4–507 of this subtitle may be: Amended only if a majority of the reasonably available members agree to the amendment; or Revoked only if: A majority of the reasonably available members agree to the revocation; or The reasonably available members are equally divided as to whether to revoke the gift. A revocation under subsection (b) of this section is effective only if, before an incision has been made to remove a part from the donor’s body or before invasive procedures have begun to prepare the recipient, the procurement organization, transplant hospital, or physician or technician knows of the revocation.