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?
Context: "Mamma Mia" is a song recorded by the Swedish pop group ABBA, written by Benny Andersson, Björn Ulvaeus and Stig Anderson, with the lead vocals shared by Agnetha Fältskog and Anni-Frid Lyngstad.  It is the opening track on the group's third album, the self-titled "ABBA".  The song's name is derived from Italian, where it is an interjection used in situations of surprise, anguish, or excitement, which corresponds to the English interjection "my" but literally means "My mommy".  The interjection "my my" can be found indeed in some lines within the song. Mamma Mia!  (promoted as Mamma Mia!  The Movie) is a 2008 British-American-Swedish musical romantic comedy film adapted from the 1999 West End/2001 Broadway musical of the same name, based on the songs of successful pop group ABBA, with additional music composed by ABBA member Benny Andersson.  The film was directed by Phyllida Lloyd and distributed by Universal Pictures in partnership with Tom Hanks and Rita Wilson's Playtone and Littlestar, and the title originates from ABBA's 1975 chart-topper "Mamma Mia".  Meryl Streep heads the cast, playing the role of single mother Donna Sheridan.  Pierce Brosnan (Sam Carmichael), Colin Firth (Harry Bright), and Stellan Skarsgård (Bill Anderson) play the three possible fathers to Donna's daughter, Sophie (Amanda Seyfried).  "Mamma Mia!"  received mixed reviews from critics and earned $609.8 million on a $52 million budget. "Super Trouper" is a single by Swedish pop group ABBA, and the title track from their 1980 studio album of the same name, written by Benny Andersson and Björn Ulvaeus.  The song – with lead vocals by Anni-Frid Lyngstad – had the working title "Blinka Lilla Stjärna", and was the last track to be written and recorded for the album (ultimately replacing the track "Put On Your White Sombrero").  "Super Trouper" is included on the compilation album "", and also features in the musical "Mamma Mia! ". ABBA (] ) were a Swedish pop group, formed in Stockholm in 1972 by members Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad.  They became one of the most commercially successful acts in the history of popular music, topping the charts worldwide from 1974 to 1982.  ABBA won the Eurovision Song Contest 1974 at The Dome in Brighton, UK, giving Sweden its first triumph in the contest, and are the most successful group to have ever taken part in the competition. Björn Kristian Ulvaeus (] ) (born 25 April 1945; credited as Björn Ulvæus) is a Swedish songwriter, producer, a former member of the Swedish musical group ABBA (1972–1982), and co-composer of the musicals "Chess", "Kristina från Duvemåla", and "Mamma Mia! ".  He co-produced the film "Mamma Mia!"  with fellow ABBA member and close friend Benny Andersson. Linda Elin Ulvaeus (born 23 February 1973) is a Swedish singer-songwriter, screen and stage actress.  She is the eldest child of Agnetha Fältskog and Björn Ulvaeus, former members of the Swedish pop group ABBA. Mamma Mia!  Original Cast Recording is the original cast album for the 1999 English stage musical "Mamma Mia! ".  The album was released in 1999 and it reached No.56 in the UK album chart, with 2 weeks on the chart.  Mamma Mia!  reinvigorated the popularity of ABBA (the film soundtrack was the best-selling album of the week and several songs made the top #75 in the UK singles chart).  The re-interest in this 1999 Original London Cast album caused it to reach #12 in the UK Album Chart, having charted at #16 a week earlier.  It features performances by the original London cast of the musical including Lisa Stokke, Siobhán McCarthy and Hilton McRae.  The album was produced by the two male members of ABBA, Benny Andersson and Bjorn Ulvaeus Mamma Mia!  (promoted as Benny Andersson & Björn Ulvaeus' Mamma Mia!  and Mamma Mia!  The Smash Hit Musical) is a jukebox musical written by British playwright Catherine Johnson, based on the songs of ABBA, composed by Benny Andersson and Björn Ulvaeus, former members of the band.  The title of the musical is taken from the group's 1975 chart-topper "Mamma Mia".  Ulvaeus and Andersson, who composed the original music for ABBA, were involved in the development of the show from the beginning.  Singer Anni-Frid Lyngstad has been involved financially in the production and she has also been present at many of the premieres around the world. Mamma Mia!  The Movie Soundtrack is the soundtrack album for the 2008 Universal Pictures musical film "Mamma Mia! ", based on the stage musical of the same name.  It features performances by the film's cast including Meryl Streep, Amanda Seyfried, Pierce Brosnan, Dominic Cooper, Stellan Skarsgård, Colin Firth, Julie Walters, Christine Baranski, Ashley Lilley, and Rachel McDowall.  The recording was produced by Benny Andersson who along with Björn Ulvaeus had produced the original ABBA recordings.  Also many of the musicians from the original ABBA recordings participated in making the soundtrack album.  In keeping with the setting, the musical arrangements featured the use of traditional Greek instruments, most noticeably the bouzouki. "Summer Night City" is a song recorded by the Swedish pop group ABBA, written by Benny Andersson and Björn Ulvaeus as a tribute to their hometown of Stockholm.  It is the group's second non-album single, released on 6 September 1978.  It was originally intended as the lead single from the group's upcoming "Voulez-Vous" album, but was eventually not included.  However, it was featured as a bonus track on the 1997 CD re-issue.
Answer: Benny Andersson