Barça beat Athletic Bilbao 4–1 in the 2009 Copa del Rey Final, winning the competition for a record-breaking 25th time. A historic 2–6 victory against Real Madrid followed three days later and ensured that Barcelona became La Liga champions for the 2008–09 season. Barça finished the season by beating the previous year's Champions League winners Manchester United 2–0 at the Stadio Olimpico in Rome to win their third Champions League title and completed the first ever treble won by a Spanish team. The team went on to win the 2009 Supercopa de España against Athletic Bilbao and the 2009 UEFA Super Cup against Shakhtar Donetsk, becoming the first European club to win both domestic and European Super Cups following a treble. In December 2009, Barcelona won the 2009 FIFA Club World Cup, and became the first football club ever to accomplish the sextuple. Barcelona accomplished two new records in Spanish football in 2010 as they retained the La Liga trophy with 99 points and won the Spanish Super Cup trophy for a ninth time.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What team did Barcelona beat to win La Liga for the 2008-09 season?
Real Madrid