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?
Facts:
ABBA was composed by Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad.
Björn Ulvaeus co-produced "Mamma mia" with close friend Benny Andersson
Answer: Benny Andersson