WORST_CASE(?,O(n^1))

Solution:
---------

  append :: [L(9) x L(14)] -(15)-> L(8)
  cons :: [Elem(9) x L(9)] -(9)-> L(9)
  cons :: [Elem(8) x L(8)] -(8)-> L(8)
  nil :: [] -(0)-> L(9)


Cost Free Signatures:
---------------------

  append :: [L_cf(0) x L_cf(0)] -(0)-> L_cf(0)
  cons :: [Elem_cf(0) x L_cf(0)] -(0)-> L_cf(0)
  nil :: [] -(0)-> L_cf(0)


Base Constructors:
------------------
  cons_L :: [Elem(1) x L(1)] -(1)-> L(1)
  nil_L :: [] -(0)-> L(1)