YES(?,O(n^1))

Problem:
 f(a(),f(a(),f(a(),f(x,b())))) -> f(f(a(),f(a(),f(a(),x))),b())
 f(f(f(a(),x),b()),b()) -> f(f(a(),f(f(x,b()),b())),b())

Proof:
 Bounds Processor:
  bound: 0
  enrichment: match
  automaton:
   final states: {3}
   transitions:
    f0(1,2) -> 3*
    f0(2,1) -> 3*
    f0(1,1) -> 3*
    f0(2,2) -> 3*
    a0() -> 1*
    b0() -> 2*
  problem:
   
  Qed