Question: Which musician, Ian Ball or Dave Mustaine, is co-founder of the American metal band Megadeth?

Context paragraphs:
United Abominations: United Abominations is the eleventh studio album by American thrash metal band Megadeth.  Released on May 8, 2007, "United Abominations" is the first Megadeth release distributed through Roadrunner Records, and with the exception of the band's frontman Dave Mustaine, was recorded with an all-new line-up.  While touring to promote the album, guitarist Glen Drover left the band for personal reasons and was replaced by Chris Broderick, leaving this as the only Megadeth studio album to which he contributed.

List of Megadeth band members: Megadeth is an American thrash metal band formed by guitarist/vocalist Dave Mustaine—after he departed from Metallica—along with bassist David Ellefson, guitarist Greg Handevidt, and drummer Dijon Carruthers, in 1983.  Early in 1984, Megadeth recorded a demo that featured new drummer Lee Rausch, who replaced Carruthers.  Slayer guitarist Kerry King covered live dates while a permanent replacement was sought.  This lineup was short-lived and after a few shows in 1984, Lee Rausch was replaced by jazz fusion drummer Gar Samuelson, in addition to the second guitarist Chris Poland.  During the Megadeth's 1985 tour promoting their debut, "Killing Is My Business... and Business Is Good! ", Poland left the band and was temporarily replaced by Mike Albert.  Poland then rejoined Megadeth in October of the same year, shortly before they began work on "Peace Sells... but Who's Buying? ".  After years of problems stemming from substance abuse, Mustaine fired both Poland and Samuelson before recording the third album "So Far, So Good... So What! "; being replaced by Jeff Young and Chuck Behler, respectively.

Peace Sells: "Peace Sells" is a song by the American thrash metal band Megadeth from the 1986 album "Peace Sells... but Who's Buying? ", written by Dave Mustaine.  It has since been a constant at Megadeth concerts.  According to Dave Ellefson it became quickly apparent when playing the song live prior to recording the album that "Peace Sells" would be a hit.  In 2006, VH1 ranked "Peace Sells" at number 11 on their list of the "40 Greatest Metal Songs" of all time.  The song is also known for the distinctive bass intro played by Ellefson.

Megadeth discography: American thrash metal band Megadeth has released fifteen studio albums, five live albums, six compilation albums, one EP, forty-seven singles, ten video albums, and thirty-six music videos.  After he was fired from Metallica in 1983, guitarist and vocalist Dave Mustaine formed Megadeth along with bassist Dave Ellefson, guitarist Greg Handevidt, and drummer Dijon Carruthers.  The band toured and gained a following, signing with the independent label Combat Records in late 1984.  Megadeth's debut album "Killing Is My Business... and Business Is Good! " (1985), sold very well for an independent release, and the group attracted the attention of major record labels.  By the end of the year, the group signed with Capitol Records.  Megadeth's first major-label album, "Peace Sells... but Who's Buying? ", was released in 1986.

Ian Ball: Ian Thomas Ball (born 19 October 1975) is an English musician, most notable for being part of the indie rock band Gomez, sharing lead vocals and guitars.  He has also performed and released two solo albums (as of June 2017).  He is also a member of the 14 piece supergroup Operation Aloha (album).  along with fellow Gomez member Olly Peacock.

Capitol Punishment: The Megadeth Years: Capitol Punishment: The Megadeth Years is a greatest hits album by heavy metal band Megadeth, released in 2000, through Capitol Records.  The album featured the Dave Mustaine/David Ellefson/Jimmy DeGrasso/Al Pitrelli line-up on the new tracks "Kill the King" and "Dread and the Fugitive Mind".  The album features a hidden track, "Capitol Punishment", which is a medley of numerous previous Megadeth songs.

That One Night: Live in Buenos Aires: That One Night: Live in Buenos Aires is a live album from American heavy metal band Megadeth which was released on CD and DVD formats.  It features a live concert recorded in Buenos Aires on October 9, 2005 at the Obras Sanitarias Stadium.  The performance is segued by cuts of Dave and Glen performing a few acoustic songs for some fans on the lawn outside of the band's hotel.  It was at this concert that Dave Mustaine announced that Megadeth would continue on past the 2005 tour.

Still Alive... and Well?: Still, Alive... and Well?  is a Megadeth compilation album released on September 10, 2002 and is the last Megadeth release with bassist and co-founder David Ellefson until his reunion with the band eight years later.  The album was released to fulfil Megadeth's record contract with Sanctuary Records after Dave Mustaine dissolved the band seemingly indefinitely when he sustained a serious nerve injury in 2002.  The album's name is a quote from Dave Mustaine's answer to an interviewer's question: "What do you want written on your tombstone?"

Dave Mustaine: David Scott Mustaine (born September 13, 1961) is an American musician, singer, songwriter, actor and author.  He is best known as the co-founder, guitarist, lead singer, and primary songwriter of the American thrash metal band Megadeth, and the original lead guitarist of the American thrash metal band Metallica.

The System Has Failed: The System Has Failed is the tenth studio album by American thrash metal band Megadeth.  Released on September 14, 2004, it was the band's second and final studio album distributed by Sanctuary Records.  "The System Has Failed" was the first album released after Mustaine recovered from his arm injury sustained in 2002 which prevented him from playing guitar.  It is also the first of three Megadeth records not to include original bassist and co-founder David Ellefson.  Instead, the album features session players, including former Megadeth guitarist Chris Poland on lead guitar.  However, Poland only provided lead guitar parts and solos on a contractual basis and did not rejoin the band.  To date, it is the only Megadeth album where the only certified member of the band was the sole Mustaine.

Supporting paragraphs: Dave Mustaine Ian Ball
Answer: David Scott Mustaine