Question:  The 2008–09 Copa del Rey final was held at a football stadium which as a seating capacity of what?
Sentence (from "2008–09 Copa del Rey"): The competition started on August 23, 2008 and concluded on May 13, 2009 with the final, held at the Mestalla Stadium in Valencia, in which Barcelona lifted the trophy for the 25th time in their history with a 4–1 victory over Athletic Bilbao, who qualified for the third qualifying round of the 2009–10 UEFA Europa League.
Relevant evidence: Yes