context:  The Patriots were hoping to stave off a losing streak and rebound from their loss to the Cardinals in this rematch of the AFC Championship. After both teams initial possession ended in punts, the Patriots drove to the Ravens 19 before settling for a Gostkowski field goal. On the first play of the Ravens' next drive, Steve Gregory intercepted Joe Flacco at the 42 and returned it 36 yards to the Ravens 6-yard line. Three plays later Brandon Bolden ran in a 2-yard touchdown, extending the lead to 10-0. Following another Ravens punt, the Patriots may have missed a chance to put the game away. After driving to the Ravens 27, an offensive pass interference penalty on Rob Gronkowski moved the ball to the Ravens 30. Then, a 19-yard reception on 2-and-11 was nullified by an offensive pass interference penalty moved the ball back to the Ravens 40, eventually ending in a 49-yard Gostkowski field goal, keeping the Ravens in the game. This time the Ravens finally managed a response driving 80 yards to score to score on a 25-yard touchdown pass from Flacco to Torrey Smith, trimming the score to 13-7. On the drive, Jerod Mayo was called for pass interference on 3rd-and-6 and Flacco completed a 14-yard pass on 3rd-and-13. Following a Patriots punt, the Ravens marched 92 yards in over 6 minutes to take a 14-13 lead on a 20-yard touchdown reception by Dennis Pitta. The Patriots took the lead right back marching 81 yards and never faced a third-down, taking the lead on a 7-yard touchdown reception by Edelman for a 20-14 halftime lead. In the second half the Ravens took the opening drive 80 yards and scored on a 7-yard touchdown run by Ray Rice to allow Baltimore to retake a 21-20 lead. Again the Patriots took the lead right back on a 12 play, 78-yard march to take a 27-21 lead on a 3-yard touchdown run by Danny Woodhead. Following a Ravens punt the Patriots drove all the way to the Ravens 2-yard line, but had to settle for a 20-yard field goal, making the score 30-21 early in the fourth quarter. The Ravens proceeded to drive to the Patriots 33, but went for it on 4th-and-1 instead of kicking the field goal and Bernard Pierce was tackled for a loss. The Ravens forced a punt and Flacco engineered a 92-yard  touchdown drive to trim the lead to 30-28 with a 5-yard touchdown pass to Smith. On the Patriots ensuing possession, Brady was intercepted by Ladarius Webb, but Webb was flagged for illegal contact and the Patriots retained possession. They reached the Ravens 44, but on 2nd-and-9, Brady was sacked for a 7-yard loss moving the ball back to the Patriots 49, and his 3rd-down pass was incomplete, forcing a punt. Taking over at their own 21 with 1:55 to go, Flacco hit Jacoby Jones for a 24-yard gain. Baltimore was able to reach the Patriots 34 where Flacco threw an incompletion on 3rd-and-9, but Devin McCourty was flagged for pass interference, moving the ball to the 7-yard line. Justin Tucker kicked a field goal that appeared to miss wide right, but was controversially ruled good and the Ravens won 31-30. With this loss New England fell to 1-2. The Ravens not only avenged the AFC Championship defeat by winning their first-ever regular season meeting against their opponent, but the Patriots faced their first sub-.500 record in 145 games since starting the 2003 season 0-1 against the Buffalo Bills, and also stumbled to their first 1-2 start since 2001. This was the fourth time in the previous ten seasons the Pats had lost consecutive games.  Also, in what turned out to be the replacement officials' next-to-last game officiating, the game was marred by a series of questionable calls that eventually provoked the Ravens fans to start chanting derogatory words towards the referees; Patriots coach Bill Belichick was seen to try to grab one of the officials as they were scurrying from the field. The Patriots were one of six 2011 season playoff teams to be under .500 after their first three games;  the others were the Steelers, Broncos, Lions, Packers, and Saints (who were sitting at 0-3 by this time).
question: How many points were the Patriots ahead by at halftime?
answer: 6