Question: title of gilbert and sullivan's last work together
[{'answer': 'The Grand Duke', 'provenance': [{'wikipedia_id': '13021', 'title': 'Gilbert and Sullivan', 'start_paragraph_id': 56, 'start_character': 915, 'end_paragraph_id': 56, 'end_character': 929, 'bleu_score': 1.0, 'section': 'Section::::Operas.:Dodging the magic lozenge.:"The Mikado".\n'}]}, {'provenance': [{'wikipedia_id': '13021', 'title': 'Gilbert and Sullivan', 'start_paragraph_id': 75, 'start_character': 0, 'end_paragraph_id': 75, 'end_character': 755, 'bleu_score': 0.9828310228624961, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8386130123406537790}, 'section': 'Section::::Operas.:Last works.\n'}]}]