MAYBE

Proof:
ConCon could not decide confluence of the system.
\cite{GNG13}, Theorem 9 does not apply.
System R transformed to optimized U(R).
Call external tool:
csi - trs 30
Input:
  ?1(z, x, z) -> b
  ?2(z, x) -> ?1(x, x, z)
  f(x) -> ?2(f(x), x)
  a -> f(a)

The external tool could not decide confluence.