An attorney currently represents the owner of a local hardware store in contract negotiations to extend the lease of the building in which the store is located. An authorized representative of a large corporation that owns and operates a nationwide chain of hardware stores has contacted the attorney about representing the store in negotiations with the neighboring property owner for an easement to gain additional access to the public roads. Without obtaining the written, informed consent of both the owner of the local store and the corporation, can the attorney agree to represent the corporation if the attorney reasonably believes that he will be able to provide competent and diligent representation to each client?