Question: who became the fifth beatle on let it be playing keyboards on the lp
[{'answer': 'Billy Preston', 'provenance': [{'wikipedia_id': '326691', 'title': 'Billy Preston', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '326691', 'title': 'Billy Preston', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 1194, 'bleu_score': 0.875122525035888, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15149027503173759334}, 'section': 'Section::::Relationship with the Beatles.\n'}]}]