The provisions of this section through those of Section 31778.2, inclusive, shall be referred to collectively as the “backward DROP provisions.” A member who retires on or after the effective date of the program may elect upon application for service or disability retirement, on a form prescribed by the board, to receive:
(a) A backward DROP payment calculated under Section 3l778.1.
(b) A monthly retirement allowance calculated as if the member had retired on the deferred retirement calculation date, except that the retirement formula applicable to the member’s service as of the election date shall be used to calculate the amount of the member’s monthly retirement allowance.