EVANSTON — The rapper from the Justin Bieber song “Baby” is officially slated to perform at A&O Ball Saturday. Reports indicate that this is also the same person who made a guest appearance in the Enrique Iglesias song “Tonight I’m Loving You.” Student reaction to the news has been mainly positive with many feeling on top of the world. RTVF freshman and A&O member Carol Lang said, “When I heard, I was like, yeah! The guy featured in that Usher