Problem:
 f(a()) -> f(f(a()))
 f(x) -> f(a())

Proof:
 Church Rosser Transformation Processor:
  
  strict:
   f(a()) -> f(f(a()))
   f(x) -> f(a())
  weak:
   
  critical peaks: 2
  f(f(a())) <-0|[]- f(a()) -1|[]-> f(a())
  f(a()) <-1|[]- f(a()) -0|[]-> f(f(a()))
  Closedness Processor (*parallel*):
   
   strict:
    
   weak:
    
   Qed