This was the second and final regular season meeting between the two teams.  The Browns snapped a four-game losing streak tothe Steelers in a 31-10 blowout victory.  They also won their first divisional game of the season, ending a five-game losing streak to division foes.  The Steelers led 3-0 after the first quarter.  However, the Browns scored 21 straight points in the second quarter, building a 21-3 halftime lead. Adding a field goal in the third quarter and a touchdown in the fourth, the Browns created an insurmountable 31-3 lead.  The Steelers' late touchdown in the fourth quarter produced the final score. Steelers' QB Ben Roethlisberger suffered only his second career loss in 20 career games against the Browns.  For Cleveland, the 21 point margin of victory was the most lopsided win over Pittsburgh since they routed them 51-0 in a Week 1 matchup during the 1989 season.  The Browns moved into third place in the AFC North with a 3-2 record while the Steelers fell into fourth place with a 3-3 record.
Question: How many points did the Browns lead by at the half?
Answer: 18