Consider the following SDT Above SDT is

• In the two rules for S
  S → 2 A C { C.x = A.x }
S → 3 A B M C { M.x = A.x + B.x }
  the action assigns attributes of RHS children (C.x, M.x) after their subtrees are complete. In an attribute grammar, actions should compute the head’s attributes (synthesized) or set inherited attributes before visiting a child. Writing to a child’s attribute at the end of the production violates both S- and L-attributed conventions.
  

• If you try to treat C.x and M.x as inherited, then their own productions also set them:
  C → 4 { C.x = 4 }, M → ε { M.x = 0 }
  which makes the same attribute both inherited and synthesized—not allowed.
  

Therefore this SDT, as stated, is not S-attributed and not L-attributed;