MAYBE

Problem:
 a(a(y,0()),0()) -> y
 c(c(y)) -> y
 c(a(c(c(y)),x)) -> a(c(c(c(a(x,0())))),y)

Proof:
 RT Transformation Processor:
  strict:
   a(a(y,0()),0()) -> y
   c(c(y)) -> y
   c(a(c(c(y)),x)) -> a(c(c(c(a(x,0())))),y)
  weak:
   
  Matrix Interpretation Processor:
   dimension: 1
   interpretation:
    [c](x0) = x0 + 9,
    
    [a](x0, x1) = x0 + x1,
    
    [0] = 9
   orientation:
    a(a(y,0()),0()) = y + 18 >= y = y
    
    c(c(y)) = y + 18 >= y = y
    
    c(a(c(c(y)),x)) = x + y + 27 >= x + y + 36 = a(c(c(c(a(x,0())))),y)
   problem:
    strict:
     c(a(c(c(y)),x)) -> a(c(c(c(a(x,0())))),y)
    weak:
     a(a(y,0()),0()) -> y
     c(c(y)) -> y
   Open