Answer based on context:

The 172nd game in the Bears-Lions rivalry took place in week four. Entering the game, the Bears held a 96-71-5 lead over the Lions, though the Lions had won the last six meetings; Chicago's last victory had been a 26-21 win in 2012. The first divisional game of the year, the Bears had struggled against NFC North teams in recent years; of their last 18 divisional matchups, they lost 14, including seven of the last nine at home. In his Keys to the Game, Jeff Joniak stated the Bears offense, once again with Brian Hoyer starting at quarterback in place of a still-healing Jay Cutler, had to hold off Teryl Austin's blitzes; the Lions had the second-highest number of blitzes in the league. While Detroit's top pass rusher Ezekiel Ansah was nursing an ankle injury, substitute Kerry Hyder recorded four sacks in his place. Joniak added the Bears could attack linebacker Tahir Whitehead, who had allowed three touchdown passes in 2016. Against a Detroit offense led by quarterback Matthew Stafford, the Bears needed to contain his targets like Marvin Jones, who had excelled over the course of the 2016 season, Pro Bowler Golden Tate, the experienced Anquan Boldin and young tight end Eric Ebron. As in previous games, third down was a critical factor in the game, Joniak stating the defense "must get off the field." After both teams exchanged punts on their first drives, the Bears scored first when Hoyer threw a four-yard touchdown pass to Eddie Royal despite being covered by Nevin Lawson. The next six series of the game ended in punts, the trend ending when the Bears were stopped on fourth down in Lions territory midway through the second quarter; Detroit eventually gained three points when Matt Prater kicked a 50-yard field goal. Connor Barth attempted his own 50-yard field goal on the next drive, but missed it wide right. With 16 seconds left in the first half, Stafford's pass for Tate was intercepted by Jacoby Glenn. The Bears were unable to turn the turnover into points as the half ended before they could score. Upon receiving the ball for the start of the second half, the Lions scored on Prater's 21-yard field goal, which the Bears responded on their following drive with Hoyer's six-yard touchdown pass to Zach Miller; the drive gained momentum when Royal recorded a 64-yard pass play, the Bears' longest play from scrimmage of the season. The Lions punted again and the Bears were able to extend their lead with their fourth quarter drive culminating in Barth's 25-yard field goal. With 4:03 left in the game, Stafford's pass for Boldin was intercepted by Deiondre' Hall, but the Lions retaliated when Andre Roberts returned a punt 85 yards for a touchdown. The Lions closed the margin to just three points when Stafford completed the two-point conversion to Tate. With the score now 17-14, the Lions attempted an onside kick, but Sam Acho recovered. Hoyer kneeled three times to seal Chicago's first win of the season.

How many field goals did Matt Prater kick?
2