YES
Did not drop rules.
Inlined conditions for 0 rules.
Left-inlined conditions for 1 rules:
  f(b()) -> a()  | 
Due to Ifrit-method removed 1 infeasible rules:
  a() -> a()  | f(a()) ->* a()
Did not use redundant rules method.
INFEASIBLE because

problem obtained from input
is proven infeasible
using TCAP on
|(f(a())) ->* |(a())

where | is used as a fresh function symbol, since it is illegal in the input format.