Question: who is the longest serving manager in man united
[{'answer': 'Sir Alex Ferguson', 'provenance': [{'wikipedia_id': '14267273', 'title': 'List of Manchester United F.C. managers', 'start_paragraph_id': 3, 'start_character': 78, 'end_paragraph_id': 3, 'end_character': 95, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '14267273', 'title': 'List of Manchester United F.C. managers', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 364, 'bleu_score': 0.9679895851501501, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13672666739995806280}, 'section': 'Section::::Abstract.'}]}]