MAYBE
MAYBE
TRS:
 {
    top(free(x)) -> top(check(new(x))),
   check(new(x)) -> new(check(x)),
  check(free(x)) -> free(check(x)),
   check(old(x)) -> old(x),
   check(old(x)) -> old(check(x)),
    new(free(x)) -> free(new(x)),
    new(serve()) -> free(serve()),
    old(free(x)) -> free(old(x)),
    old(serve()) -> free(serve())
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
      top(free(x)) -> top(check(new(x))),
     check(new(x)) -> new(check(x)),
    check(free(x)) -> free(check(x)),
     check(old(x)) -> old(x),
     check(old(x)) -> old(check(x)),
      new(free(x)) -> free(new(x)),
      new(serve()) -> free(serve()),
      old(free(x)) -> free(old(x)),
      old(serve()) -> free(serve())
   }
  Fail