After winning at home, the Steelers traveled to Cincinnati for Game 2 against the Bengals. Before the game started there were an altercation between the two teams during warmups. Vince Williams and Vontaze Burfict were in the center of the scuffle. The game began with a score on the very first drive, when DeAngelo Williams ran for a 1-yard TD for a 7-0 lead and would increase their lead in the 2nd quarter, when Chris Boswell went for 2 field goals:  From 42 and 47 yards out for 10-0 and 13-0 leads.  QB Andy Dalton would be knocked out of the game so backup QB AJ McCarron came in and threw his first career TD pass to A. J. Green from 66 yards out to make the score 13-7.  Boswell, however, wrapped up the scoring of the first half with another 47 yard field goal for a 16-7 lead at halftime.  In the third quarter, the Steelers went back to work as William Gay picked off AJ McCarron and returned it 23 yards for a TD for a 23-7 game.  Mike Nugent would kick a 46-yard field goal to make it 23-10.  The Steelers went back to work in the fourth quarter when Boswell kicked a 31-yard field goal for a 26-10 game.  The Bengals responded with Nugent kicking a 27-yard field goal for a 26-13 game.  Later on however, the Steelers would pretty much seal the game when Williams ran for another 1-yard TD for a 33-13 game.  The Bengals would wrap up the scoring of the game when McCarron found Rex Burkhead on a 5-yard pass for a 33-20 final score. With the win, the Steelers improved to 8-5.  The defense also stood out and continued their reign of sacks and takeaways with 3 each (picked off Dalton once, picked off McCarron twice).
Question: How many points were the Steelers leading by at half time?
Answer: 9