Question: when did the battle of atlantic start and end
[{'answer': 'September 3 , 1939', 'provenance': [{'wikipedia_id': '57765', 'title': 'Battle of the Atlantic', 'start_paragraph_id': 206, 'start_character': 255, 'end_paragraph_id': 206, 'end_character': 273, 'bleu_score': 1.0, 'section': 'Section::::Civilian experience.\n'}]}, {'answer': 'May 8 , 1945'}]