Task: Question Understanding
Input (English): Passage: Ryan Mallett was given the starting quarterback position against the Panthers. The Texans only lead of the game came in the first quarter following a 43-yard field goal from Randy Bullock. Following 10 unanswered points from Carolina in the 2nd quarter, Houston trailed 3-10 going into halftime. Early in the third quarter Houston tied the game at 10 a piece. A Carolina touchdown late in the 3rd quarter and another early in the 4th sealed a Panthers victory as the Texans couldn't manage a comeback. With the loss Houston dropped to 0-2, their worst start since the 2008 season.
Question: How many points was Carolina leading by at halftime?
Output (English): number