Question: Björn Ulvaeus was a part of a Swedish pop group, formed in Stockholm in 1972, as well as co-producer on the film "Mamma Mia!" with who?
{'answer': 'Benny Andersson', 'supporting_facts': [['ABBA', 0], ['Björn Ulvaeus', 0], ['Björn Ulvaeus', 2], ['Björn Ulvaeus', 3]]}