Question: who was the oldest serving president of the united states
[{'answer': 'Ronald Reagan', 'provenance': [{'wikipedia_id': '11262088', 'title': 'List of presidents of the United States by age', 'start_paragraph_id': 3, 'start_character': 460, 'end_paragraph_id': 3, 'end_character': 473, 'bleu_score': 1.0, 'section': 'Section::::Age of presidents.\n'}]}, {'provenance': [{'wikipedia_id': '11262088', 'title': 'List of presidents of the United States by age', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 531, 'bleu_score': 0.7851324905260421, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16245819890330413719}, 'section': 'Section::::Age of presidents.\n'}]}]