Coming off their thrilling home win over the Ravens, the Vikings flew to Heinz Field for a Week 7 interconference duel with the defending Super Bowl champion Pittsburgh Steelers. Minnesota trailed late in the first quarter as Steelers kicker Jeff Reed got a 39-yard field goal, but they took the lead in the second quarter as running back Adrian Peterson got a 1-yard touchdown. However, Pittsburgh retook the lead as quarterback Ben Roethlisberger hooked up with wide receiver Mike Wallace on a 40-yard touchdown pass. Both teams exchanged field goals in the third quarter as Reed nailed a 27-yard field goal, while Vikings kicker Ryan Longwell booted an 18-yard field goal. In the fourth quarter, Minnesota began to trail big as Vikings quarterback Brett Favre was stripped by defensive end Brett Keisel, causing a 77-yard fumble return for a touchdown by linebacker LaMarr Woodley. The Vikings immediately struck back with rookie wide receiver Percy Harvin's 88-yard kickoff return for a touchdown, but the Steelers' defense answered right back with linebacker Keyaron Fox's 82-yard interception return for a touchdown. The Vikings could not come back to win. The Steelers ended up winning 27-17.
Question: how many yards did keisel fumble?
Answer: 77