Definition: Given a list of steps and an additional step, determine where the step fits into the original list of steps. A correct answer, correctly places the given step into the set of steps so that it creates a new plausible set of steps. Output must be formatted as 'After step n', where n is the step number after which the given additional step is to be inserted.
Input: Steps: (1) A plant dies (2) The remains of the plant are buried very fast in sediment (3) The soft parts of the plant decay (4) The hard parts of the plant are replaced with minerals (5) The rock erodes (6) The fossil appears on the surface of the ground.  
Where does the following step fit into the given list of steps: The sediment turns into rock 
Output:
 After step 4. 