Total of 12 points.

Assuming they strictly follow the suggestions, count them the following way.
If they don't, do what seems appropriate based on this.

1.5  data representation of a state, helper functions to manipulate states
1    initial & final state
1    function: state -> list of successor states
      domain knowledge
1.5  function: list of states -> list of successor states
      foldr
1    function: state -> boolean (legal state?)
      domain knowledge
1.5  function: list of states -> list of legal states
      filter
1    function: state -> boolean (final state?)
      domain knowledge
1.5  function: list of states -> list of final states
      filter
2    function: finding solution given these pieces

Don't forget the standard guidelines for templates, testing, etc.

They don't need to use abstract functions, although point out where they could.

A nonworking program can get up to 9 points.