Following their victory over the Patriots, the Steelers remained at home the next week for their second match-up of the season against division rivals the Baltimore Ravens.  The Ravens scored first with an 18-yard field goal by kicker Billy Cundiff, the only points scored in the first quarter by either team.  Steelers kicker Shaun Suisham answered with a 36-yard field goal early in the second quarter, and a 30-yard field goal near the end, but both of these were quickly matched by Baltimore's Cundiff with a 43-yard and 51-yard field goal, respectively, giving Baltimore a 9-6 lead at halftime.  The Ravens then increased their lead in the third quarter when Ray Rice scored the first touchdown of the game on a 4-yard run.  The Steelers rallied hard in the fourth quarter, with running back Rashard Mendenhall making a 1-yard run to score a touchdown, and then taking the lead for the first time in the game when quarterback Ben Roethlisberger made a successful 25-yard pass to wide receiver Mike Wallace in the endzone for a second touchdown.  On their final drive of the game, the Steelers were ready to potentially increase their lead with a 47-yard field goal kick by Shaun Suisham, but a 5-yard delay of game penalty put them out of field goal range and they were instead forced to punt the ball to the Ravens.  The Ravens then began a 92-yard drive, culminating in a 26-yard touchdown pass by quarterback Joe Flacco to wide receiver Torrey Smith in the endzone with just 8 seconds remaining, giving them the game.
Question: How many more field goals were made in the first half than the second?
Answer: 4