Question: when was the empire state building started and finished
[{'answer': 'March 17 , 1930', 'provenance': [{'wikipedia_id': '9736', 'title': 'Empire State Building', 'start_paragraph_id': 2, 'start_character': 478, 'end_paragraph_id': 2, 'end_character': 493, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'April 11 , 1931', 'provenance': [{'wikipedia_id': '9736', 'title': 'Empire State Building', 'start_paragraph_id': 28, 'start_character': 891, 'end_paragraph_id': 28, 'end_character': 906, 'bleu_score': 1.0, 'section': 'Section::::History.:Construction.\n'}]}]