Question: when was the excalibur built in las vegas
[{'answer': '1990', 'provenance': [{'wikipedia_id': '705291', 'title': 'Excalibur Hotel and Casino', 'start_paragraph_id': 6, 'start_character': 73, 'end_paragraph_id': 6, 'end_character': 77, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '705291', 'title': 'Excalibur Hotel and Casino', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 343, 'bleu_score': 0.965203995518735, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16819113457514232920}, 'section': 'Section::::History.\n'}]}]