Question: when did ben stone leave law and order
[{'answer': '1994', 'provenance': [{'wikipedia_id': '1840876', 'title': 'Benjamin Stone (Law & Order character)', 'start_paragraph_id': 18, 'start_character': 666, 'end_paragraph_id': 18, 'end_character': 670, 'bleu_score': 1.0, 'section': 'Section::::Reason for departure.\n'}]}]