Coming off their divisional win over the Browns, the Steelers stayed at home for a Week 7 interconference duel with the 6-0 Minnesota Vikings.  Pittsburgh got the game's opening score late in the first quarter with kicker Jeff Reed nailing a 39-yard field goal.  The Vikings would answer in the second quarter with a 2-yard touchdown run from running back Adrian Peterson, yet the Steelers struck back with Ben Roethlisberger completing a 40-yard touchdown pass to rookie wide receiver Mike Wallace. Both teams would swap field goals in the third quarter, with Reed booting a 27-yard field goal and Vikings kicker Ryan Longwell making an 18-yard field goal.  In the fourth quarter, Pittsburgh defense came up with a huge play as defensive end Brett Keisel forced a fumble off of Vikings quarterback Brett Favre, allowing linebacker LaMarr Woodley to return the fumble 77&#160;yards for a touchdown.  However, Minnesota immediately struck back as wide receiver Percy Harvin returned a kickoff 88&#160;yards for a touchdown. The Steelers' defense came up big again as linebacker Keyaron Fox returned a Favre interception 82&#160;yards for a touchdown. With the win, Pittsburgh went into their bye week at 5-2 while Minnesota dropped to 6-1.
Question: how many yards was the vikings touchdown run?
Answer: 2