YES(?,O(n^1))

Problem:
 g(b()) -> f(b())
 f(a()) -> g(a())
 b() -> a()

Proof:
 Bounds Processor:
  bound: 2
  enrichment: match
  automaton:
   final states: {5}
   transitions:
    a1() -> 10*
    g1(10) -> 11*
    f1(8) -> 9*
    b1() -> 8*
    a2() -> 14*
    g0(5) -> 5*
    g2(18) -> 19*
    b0() -> 5*
    f0(5) -> 5*
    a0() -> 5*
    9 -> 5*
    10 -> 5*
    11 -> 5*
    14 -> 18,8
    19 -> 9,5
  problem:
   
  Qed