Question: who wrote the song let's call the whole thing off
[{'answer': 'George Gershwin and Ira Gershwin', 'provenance': [{'wikipedia_id': '7401439', 'title': "Let's Call the Whole Thing Off", 'start_paragraph_id': 1, 'start_character': 54, 'end_paragraph_id': 1, 'end_character': 86, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7401439', 'title': "Let's Call the Whole Thing Off", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 366, 'bleu_score': 0.819480769858081, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1679234130495444318}, 'section': 'Section::::Abstract.'}]}]