Question: What number album was released on 4 April 2014 in Europe by a Dutch symphonic metal band formed in 2002 by former Within Temptation keyboardist Martijn Westerholt, and Charlotte Wessels?

Context articles: Robert Westerholt
The Human Contradiction
Charlotte Wessels
Within Temptation
The Silent Force
Sharon den Adel
Delain
Enter (Within Temptation album)
Martijn Westerholt
Amenity (demo)

Robert Westerholt (born 2 January 1975 in Waddinxveen, South Holland, Netherlands) is a Dutch musician, known as the guitarist, unclean vocalist and co-founder of the symphonic metal band Within Temptation.
 He also writes music for the band along with his partner and band vocalist Sharon den Adel.
 He used to work in human resource management before his career with Within Temptation.
The Human Contradiction is the fourth studio album by the Dutch symphonic metal band Delain.
 It was released on 4 April 2014 in Europe, and on 8 April 2014 in North America.
Johanna Charlotte Wessels (born 13 May 1987) is a Dutch singer-songwriter who was born in Zwolle, Netherlands.
 Best known as the lead vocalist for the Dutch symphonic metal band Delain.
 She is also in the symphonic rock musical group called Phantasma.
Within Temptation is a Dutch symphonic metal band founded in April 1995 by vocalist Sharon den Adel and guitarist Robert Westerholt.
 They have always been classified by critics as gothic metal, although the "gothic" influence varies with each album.
 Their most prominent and well-known sound is described as symphonic metal, although their earlier material, such as debut album "Enter", was mostly gothic metal.
 "Enter" even had a hint of doom metal.
 In an interview, Den Adel said they fell into a symphonic rock genre with various influences.
 In a later interview with Dutch music platform 3VOOR12, den Adel stated that "we consider ourselves more a symphonic rock band ... in my opinion, we are no gothic band".
The Silent Force is the third studio album by Dutch symphonic metal band Within Temptation, released on 15 November 2004, by GUN Records.
 This album is the first to feature Ruud Jolie on lead guitar, as well as Martijn Spierenburg on keyboards, after Martijn Westerholt had to leave the band due to illness.
Sharon Janny den Adel (born 12 July 1974) is a Dutch singer, songwriter and fashion designer, best known as the lead vocalist and one of the main songwriters in the Dutch symphonic metal band Within Temptation.
 She has been a performing musician since the age of 14, and was a founding member of Within Temptation, along with Robert Westerholt, in 1996.
Delain is a Dutch symphonic metal band formed in 2002 by former Within Temptation keyboardist Martijn Westerholt, and Charlotte Wessels.
 The name of the band comes from the Kingdom of Delain in Stephen King's novel, "The Eyes of the Dragon".
Enter is the debut studio album by Dutch symphonic/gothic metal band Within Temptation, released by DSFA Records in 1997.
 The album prominently features lead singer Sharon den Adel's vocals as well as guitarist Robert Westerholt's gruff death metal growls.
 Lex Vogelaar, founder of the Dutch death metal band Orphanage, supplied the guitar parts for "Pearls of Light", as well as producing the album, and Orphanage vocalist George Oosthoek performed some of the growls on "Deep Within".
David Martijn Westerholt (born 30 March 1979 in Waddinxveen, Netherlands) is the cofounder (along with Charlotte Wessels), keyboardist, and the main songwriter of the Dutch symphonic metal band Delain.
 He was previously a member of symphonic metal band Within Temptation, until he was diagnosed with infectious mononucleosis shortly after the release of Within Temptation's second full-length studio album, "Mother Earth".
 His brother Robert Westerholt is the guitarist and founder of Within Temptation.
 He currently lives in Zwolle, where he resides since his study in Communication at Windesheim College in 1998.
Amenity is the first demo of the Dutch Symphonic metal band Delain.
 It was released in 2002.
 Martijn Westerholt, founder of Delain, doesn't regard this as the beginning of Delain: "I tried a few songs with local musicians, but it did not work, it did not really bring me what I was looking for."