YES(?,O(n^1))

Problem:
 b(a(b(x1))) -> a(b(a(x1)))
 b(b(a(x1))) -> b(b(b(x1)))
 c(a(x1)) -> a(b(c(x1)))
 c(b(x1)) -> b(a(c(x1)))

Proof:
 Bounds Processor:
  bound: 2
  enrichment: match
  automaton:
   final states: {3,2}
   transitions:
    a1(6) -> 7*
    b1(5) -> 6*
    c1(4) -> 5*
    a2(12) -> 13*
    a2(14) -> 15*
    b0(1) -> 2*
    b2(13) -> 14*
    a0(1) -> 1*
    c0(1) -> 3*
    1 -> 4*
    5 -> 12*
    7 -> 5,3
    15 -> 6*
  problem:
   
  Qed