When the charge is received in the Regional Office it is filed, docketed, and assigned a case number. The Regional Director may cause a copy of the charge to be served on the person against whom the charge is made, but timely service of a copy of the charge within the meaning of the proviso to section 10(b) of the Act is the exclusive responsibility of the charging party and not of the Regional Director. The Regional Director requests the person filing the charge to submit promptly evidence in its support. As part of the investigation hereinafter mentioned, the person against whom the charge is filed, hereinafter called the respondent, is asked to submit a statement of position in respect to the allegations. The case is assigned for investigation to a member of the field staff, who interviews representatives of the parties and other persons who have knowledge as to the charge, as is deemed necessary. In the investigation and in all other stages of the proceedings, charges alleging violations of section 8(b)(4) (A), (B), and (C), charges alleging violations of section 8(b)(4)(D) in which it is deemed appropriate to seek injunctive relief under section 10(1) of the Act, and charges alleging violations of section 8(b)(7) or 8(e) are given priority over all other cases in the office in which they are pending except cases of like character; and charges alleging violations of sections 8(a)(3) or 8(b)(2) are given priority over all other cases except cases of like character and cases under section 10(1) of the Act. The Regional Director may exercise discretion to dispense with any portion of the investigation described in this section as appears necessary in consideration of such factors as the amount of time necessary to complete a full investigation, the nature of the proceeding, and the public interest. After investigation, the case may be disposed of through informal methods such as withdrawal, dismissal, or settlement; or the case may necessitate formal methods of disposition. Some of the informal methods of handling unfair labor practice cases will be stated first.