After a tough win on the road, the Steelers went back home for their second game of the season against the Ravens. Pittsburgh scored first in the first quarter when Ben Roethlisberger found Le'Veon Bell for a 20-yard pass to make it 7-0 and the only score of the period. In the second quarter, the Steelers moved up 14-0 when Bell ran for a 1-yard touchdown. The Ravens got on the board when Joe Flacco found Chris Moore on a 30-yard pass to make it 14-7. The Steelers then moved ahead by double digits again when Chris Boswell put up a 52-yard field goal to make it 17-7. The Ravens then came within 3 when Alex Collins ran for an 18-yard touchdown to make the score 17-14. The Steelers closed out the half with another field goal kicked by Boswell from 43 yards out to make it 20-14 at halftime. In the third quarter, it was all Ravens when they took the lead after scoring 3 times: First when Justin Tucker managed to nail a 47-yard field goal to make it 20-17. This would be followed by Javorious Allen's 1-yard touchdown run as they took the lead 24-20. Flacco then found Patrick Ricard on a 6-yard pass as the Ravens moved up by double digits 31-20. In the fourth quarter, the Steelers managed to come within 2, starting with a 24-yard field goal kicked by Boswell shortening the Ravens' lead to 31-23. This would then be followed up by Roethlisberger connecting with Roosevelt Nix on a 1-yard pass (with a failed 2-point conversion) to make it 31-29. The Ravens managed to pull away when Allen ran for a 9-yard touchdown to make it 38-29. The Steelers then completed the comeback when Bell ran for an 11-yard touchdown to make it 38-36. This would be followed by Boswell kicking a 46-yard field goal to make it 39-38. The Ravens then got the ball back, but Flacco was sacked by T. J. Watt as time expired, sealing the win for the Steelers. With the win, the Steelers improved to 11-2 and were awarded the AFC North division title. The team also managed to win their 9th straight game over a divisional opponent. Pittsburgh notched their first 3-game win streak over the Ravens since defeating them three times during the 2008 season (including the playoffs). The teams' 77 combined points marked the most in series history. The team also swept the Ravens for the first time since 2008.  With the division clinched, the team would win consecutive titles for the first time since the 2007 and 2008 seasons. The Steelers' second consecutive 11+ point comeback victory marked the first time the Steelers had accomplished this feat since coming back from down 14 against the Denver Broncos on December 7, 1997 and then again from down 14 against the New England Patriots on December 13, 1997.

Based on the above article, answer a question. How many field goals did Boswell kick in the first half?
2