code: def word_intersection( word_a, word_b ):
      
      positions = []
      word_a_letters = get_letters( word_a )
      word_b_letters = get_letters( word_b )
      for idx,wa in enumerate(word_a_letters):
          for idy,wb in enumerate(word_b_letters):
              if ( wa == wb ):
                  positions.append( (idx, idy) )
      return positions
docs: return a list of tuples where word_a, word_b intersect