(a) The department shall issue a one-time increase in the amount of six hundred dollars ($600) to a payment received under this chapter as of the eligibility date to be determined by the department.
(b) The one-time increase to a payment made pursuant to this section shall be exempt from the administration provisions pursuant to Article 3 (commencing with Section 12100) and shall be administered in the form and manner determined by the department.
(c) Notwithstanding the rulemaking provisions of the Administrative Procedure Act (Chapter 3.5 (commencing with Section 11340) of Part 1 of Division 3 of Title 2 of the Government Code), the department may implement, interpret, or make specific this section by means of all-county letters or similar written instructions, which shall be exempt from submission to or review by the Office of Administrative Law. These all-county letters or similar instructions shall have the same force and effect as regulations.