Question: how many air force bases are there in the usa
[{'answer': '59', 'provenance': [{'wikipedia_id': '322064', 'title': 'List of United States Air Force installations', 'start_paragraph_id': 3, 'start_character': 114, 'end_paragraph_id': 3, 'end_character': 116, 'bleu_score': 1.0, 'section': 'Section::::United States Active Duty.\n'}]}, {'provenance': [{'wikipedia_id': '322064', 'title': 'List of United States Air Force installations', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 148, 'bleu_score': 0.9214109120166031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7559860553011925874}, 'section': 'Section::::United States Active Duty.\n'}]}]