(2012 Detroit Lions season) After defeating the Jaguars at home in overtime, the Texans traveled to Detroit to play in their first ever Thanksgiving Day game.  Many touchdowns were scored between both of the teams, but the Texans got the better edge of it when Justin Forsett ran for a controversial touchdown from deep in the Texans' territory.  With their 2nd-straight overtime victory, the Texans improved to 10-1, 1-0 on Thanksgiving, and 2-1 against the Lions all-time. Mikel Leshore of Detroit struck first to make it 7-0. In the 2nd,   Arian Foster scored to make it 7-7. Mike Thomas caught to make it 14-7 Detroit. Matt Schaub then hit Owen Daniels to make it 14-14. 2 plays later Calvin Johnson caught it to make it 21-14 Lions at the half. Jason Hanson made one to make it 24-14. Then Justin Forsett scored on an 81-yard run that clearly showed that Forsett was down by contact, but was illegally challenged; it  made it 24-21. Shayne Graham would follow suit with a 45-yard FG to tie it at 24, but Detroit would retake the lead early in the 4th quarter with a Joique Bell 23-yard TD run to make the score 31-24. Foster scored his 2nd TD late in regulation to tie the game at 31. The Texans got the last laugh as Graham would nail the 32-yard game-winner with 2:21 left in overtime to win the game 34-31.
Question: How many points were the Lions leading by at the half?
Answer: 7