In what year was the album “So Cool” released by 씨스타?

In what year was the album “So Cool” released by 씨스타?: The album “So Cool” was released in 2011 by 씨스타, featuring 12 tracks.
What is the most successful song from the album “So Cool” by 씨스타?: “So Cool” is the biggest hit from the album “So Cool” by 씨스타.

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