First(A) = {a,c}
First(B) = {b,c}
S → A | B ===> First(A) ∩ First(B) ≠ ∅ ===> it can't be LL(1)
Checking LR(1) or NOT ? just construct LR(1) items
Item 0 :-
S' → S, \$
S → .A, \$
S → .B, \$
A → .a, \$
A → .c, \$
B → .b, \$
B → .c, \$
on this item, with terminal c, we will go to, let Item K,
Item K :-
A → c., \$
B → c., \$
Which is Reduce - Reduce Conflict ==> can't be parsed by LR(1)
PS :- the string "c" have more than one Left Most derivation ==> Ambiguous grammar ==> can't be either LL(1) or LR(1)