Question: when did the united states pull out of the vietnam war
[{'answer': '29 April 1975', 'provenance': [{'wikipedia_id': '32611', 'title': 'Vietnam War', 'start_paragraph_id': 136, 'start_character': 46, 'end_paragraph_id': 136, 'end_character': 59, 'bleu_score': 1.0, 'section': 'Section::::U.S. exit and final campaigns, 1973–75.:Fall of Saigon.\n'}]}, {'provenance': [{'wikipedia_id': '32611', 'title': 'Vietnam War', 'start_paragraph_id': 136, 'start_character': 0, 'end_paragraph_id': 136, 'end_character': 546, 'bleu_score': 0.9560664034215631, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1656018429898568517}, 'section': 'Section::::U.S. exit and final campaigns, 1973–75.:Fall of Saigon.\n'}]}]