Question:  The 2008–09 Copa del Rey final was held at a football stadium which as a seating capacity of what?

Context paragraphs:
2013 Copa del Rey Final: The 2013 Copa del Rey Final was the 111th final since its establishment.  The match was a Madrid derby between Real Madrid and Atlético Madrid on 17 May 2013 at the Santiago Bernabéu Stadium in Madrid.  It was the clubs' first meeting in the final since the 1992 final when Atlético won 2–0 over Real Madrid.  Before this match, the two teams have been finalists on four other occasions in 1960, 1961 and 1975 Copa del Rey; all Atlético wins; except 1975 when Real Madrid won.  Atlético lifted the trophy for the tenth time in their history.

2015 Supercopa de España: The 2015 Supercopa de España was a two-legged football match-up that was played in August 2015 between Athletic Bilbao, runners-up of the 2014–15 Copa del Rey, and Barcelona, the champions of 2014–15 La Liga and the 2014–15 Copa del Rey.  It was also a repetition of the 2015 Copa del Rey Final.

2009 Supercopa de España: The 2009 Supercopa de España was two-legged Spanish football match-up played on 16 August and 23 August 2009.  It was contested by Athletic Bilbao, the 2008–09 Copa del Rey runners-up, and Barcelona, the 2008–09 Primera División and 2008–09 Copa del Rey winners.

1992 Copa del Rey Final: The 1992 Copa del Rey Final was the 90th final of the Copa del Rey.  The final was played at Santiago Bernabéu Stadium in Madrid, on 27 June 1992, being won by Atlético Madrid, who beat Real Madrid 2–0.

2011 Copa del Rey Final: The 2011 Copa del Rey Final was the 109th final since its establishment.  The match was a traditional 'El Clásico' rivalry between Barcelona and Real Madrid which took place on 20 April 2011 at the Mestalla Stadium, making it the sixth such Copa del Rey final (the last one was played also in Valencia on 5 April 1990), just four days after the two teams played each other in La Liga and seven days before they played each other in the UEFA Champions League first leg semi-final.

2008–09 Copa del Rey: The 2008–09 Copa del Rey was the 107th staging of the 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.  The defending cup holders were Valencia, but they were eliminated in the quarter-finals.

2016 Copa del Rey Final: The 2016 Copa del Rey Final was a football match played on 22 May 2016 to decide the winner of the 2015–16 Copa del Rey, the 114th edition of Spain's primary football cup.  It was played at the Vicente Calderón Stadium in Madrid.

Mestalla Stadium: Mestalla Stadium (Spanish: "Estadio de Mestalla" ] , ] ) is a football stadium in Valencia, Spain.  The stadium is the home ground of Valencia Club de Fútbol and has a capacity of 49,500 seats.

2015 Copa del Rey Final: The 2015 Copa del Rey Final was a football match on 30 May 2015 to decide the winner of the 2014–15 Copa del Rey, the 113th edition of the Copa del Rey, Spain's primary football cup.

2014 Copa del Rey Final: The 2014 Copa del Rey Final was the 112th final of Spain's premier football cup since its establishment.  The match was an "El Clásico" between Real Madrid and Barcelona on 16 April 2014 at Mestalla in Valencia, making it the seventh such Copa del Rey final (the last one was also played at the Mestalla on 20 April 2011).  Real Madrid won the cup for the 19th time after a 2–1 win.

Supporting paragraphs: 2008–09 Copa del Rey Mestalla Stadium
Answer: 49,500