Difficulty calculating LL1 grammar tracking

S → L r

L → A B | B

A → D

D → a | c L

B → | d L | b

Fo (S) = {$}
It is there that I have problems, what I wrote does not seem to me well.
To calculate Fo (L), I need Fo (D) and Fo (B), but to calculate Fo (D)
I need Fo (L), same for Fo (B), what am I doing wrong?


Fo (L) = {r} U Fo (D) U Fo (B) =
Fo (A) = First (B) U Fo (L) = {d, b, r, ...}
Fo (D) = Fo (A) U Fo (L) = Fi (B) U Fo (L)
Fo (B) = Fo (L) =

Thank you