Question: How many members were in the South Korean boy group whose first official sub-unit is Bastarz?

Passages:
"Hey Mama" is the debut single by EXO-CBX, the first official sub-unit of the South Korean boy group EXO.  It was released on October 31, 2016 by S.M. Entertainment as the title track of their debut extended play "Hey Mama! ".  The Japanese version of the song was released on May 24, 2017 along with their Japanese debut EP "Girls". Hey Mama!  is the debut extended play by EXO-CBX, the first official sub-unit of the South Korean boy group EXO.  It was released on October 31, 2016 by S.M. Entertainment under distribution by KT Music.  The EP features five tracks in total with a variety of genres. Infinite H (Korean: 인피니트H ) is the first official sub-unit of South Korean boy group Infinite formed under Woollim Entertainment in 2013.  The sub-group consists of Infinite members Dongwoo and Hoya.  The sub-unit debuted with their mini album titled Fly High in January 2013. Bastarz (Korean: 바스타즈; stylized BASTARZ) is the first official sub-unit of the South Korean boy group Block B.  Established in April 2015, the sub-unit consists of three members: Block B's two main dancers, B-Bomb and U-Kwon, and the rapper P.O.  The sub-unit debuted with their first mini album, entitled "Conduct Zero," on April 14, 2015, and released their second mini album, "Welcome 2 Bastarz," on October 31, 2016. "Ka-CHING!"  is the Japanese debut single by EXO-CBX, the first official sub-unit of the South Korean boy group EXO.  It was officially released on May 24, 2017 by Avex Trax as the title track of their debut Japanese extended play "Girls".  The song was first revealed in the short version of the music video on May 1. Girls is the debut Japanese extended play by EXO-CBX, the first official sub-unit of the South Korean boy group EXO.  It was released on May 24, 2017 by Avex Trax and distributed by Avex Music Creative.  The EP features seven tracks in total including the Japanese version of their debut Korean single "Hey Mama!"  and a bonus track that will be included only in the first edition of the album. VIXX LR (Korean: 빅스 LR ) is the first official sub-unit of South Korean boy band VIXX formed by Jellyfish Entertainment.  Established in August 2015, VIXX LR consists of VIXX's main vocalist Leo and main rapper Ravi.  The sub-unit debuted with their first mini album, titled "Beautiful Liar" on August 17, 2015. Block B (Korean: ) is a South Korean boy group created by Cho PD in 2011.  The group consists of seven members: Taeil, B-Bomb, Jaehyo, U-Kwon, Park Kyung, Zico and P.O. Jung Taek-woon (Hangul: 정택운 , born on November 10, 1990), better known by his stage name Leo (Hangul: 레오 ), is a South Korean singer, songwriter and musical theatre actor, signed under Jellyfish Entertainment.  Known for his high-pitched, sharp, and clear vocals, Leo debuted as a member of the South Korean boy group VIXX in May 2012, and began his acting career in 2014 in the musical "Full House" as Lee Young-jae.  In 2015 he began his songwriting career, and with VIXX member Ravi formed VIXX's first official sub-unit VIXX LR. EXO-CBX (, also known as CBX or ChenBaekXi) is the first official sub-unit of South Korean boy group EXO.  Formed by S.M. Entertainment in 2016, the group is composed of three EXO members: Chen, Baekhyun, and Xiumin.  Their debut extended play "Hey Mama! " was released in October 2016.

Supporting sentences:
Bastarz (Korean: 바스타즈; stylized BASTARZ) is the first official sub-unit of the South Korean boy group Block B.  The sub-unit debuted with their first mini album, entitled "Conduct Zero," on April 14, 2015, and released their second mini album, "Welcome 2 Bastarz," on October 31, 2016.  The group consists of seven members: Taeil, B-Bomb, Jaehyo, U-Kwon, Park Kyung, Zico and P.O.