Following a close victory over the Chargers, the Steelers traveled to Ford Field for a Week 5 interconference duel with the 1-3 Detroit Lions.  Despite the Lions getting the opening score of the first quarter with a 46-yard field goal from kicker  Jason Hanson, Pittsburgh would answer with running back Rashard Mendenhall's 7-yard touchdown run.  Afterwards, Detroit closed out the opening period with Hanson making another 46-yard field goal.  In the second quarter, the Steelers would deliver a big strike with quarterback Ben Roethlisberger completing a 15-yard touchdown pass to tight end Heath Miller.  Even though the Lions came right back with cornerback Williams James returning an interception 38&#160;yards for a touchdown, Pittsburgh effectively replied with Roethlisberger's 17-yard touchdown pass to wide receiver Hines Ward. In the third quarter, the Steelers would add onto their lead as Roethlisberger threw to rookie wide receiver Mike Wallace on a 47-yard touchdown pass.  Detroit tried to rally in the fourth quarter as quarterback Daunte Culpepper found wide receiver Dennis Northcutt on a 25-yard touchdown pass, but Pittsburgh's defense made a crucial stand with three-straight sacks (courtesy of linebacker LaMarr Woodley, cornerback William Gay, and linebacker Lawrence Timmons), followed by cornerback Ike Taylor swatting away the Lions' last hope from a hail-mary pass.
Question: How many of the touchdowns were passing touchdowns?
Answer: 4