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

Proof:
 Uncurry Processor:
  f4(f(),b()) -> c()
  c() -> c()
  f4(f(),c()) -> b()
  a() -> b()
  Ground Confluence Processor:
   confluent by decision procedure.