Context: After the win at home against the Bengals, the Steelers traveled to take on the Packers in a rematch of Super Bowl XLV.  Coming into this game with a record of 2-5 in road games, the Packers scored first when Matt Flynn found Jarrett Boykin on a 5-yard pass for a 7-0 lead.  The Steelers managed to tie it up late in the first quarter when Ben Roethlisberger found Emmanuel Sanders on a 1-yard pass taking the game to 7-7.  In the 2nd quarter, the Packers retook the lead as Eddie Lacy ran for a 14-yard touchdown making the score 14-7.  This was followed up by the Steelers coming within 4 as Suisham kicked a 31-yard field goal as for a 14-10 score at halftime.  After the break, the Steelers took the lead as Roethlisberger rushed for a touchdown himself from 13 yards out making the score 17-14.  The Packers took the lead back as Lacy ran for a 2-yard touchdown making the score 21-17.  The Steelers then moved back into the lead as Roethlisberger found Matt Speath on an 11-yard pass making the score 24-21 and then Cortez Allen picked off Matt Flynn returning the ball 40 yards for a touchdown making the score 31-21.  In the 4th quarter, the Packers tried a comeback attempt as Mason Crosby nailed a 22-yard field goal to come within 7 31-24.  Eventually, they managed to tie the game when John Kuhn ran for a 1-yard touchdown at 31-31.  The Steelers moved back into the lead as Le'Veon Bell ran for a 1-yard touchdown for a 38-31 lead.  Matt Flynn moved the Packers down the field but his last attempt within the final 3 seconds was incomplete sealing the win for the Steelers as they improved to 7-8 while finishing 3-5 in road games.

Question: How many points were the Packers leading by at halftime?

Answer:
4