user: Question: What was the challenge for episode 28?
Columns: ['Episode Number', 'Location', 'Original Airdate', 'Challenge Winner', 'Challenge']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [20.0, 'Las Vegas , Nevada', 'August 12, 2009', 'Food', '6-pound "Big Badass Burrito"']
SQL:

assistant: SELECT "Challenge" FROM "Table" WHERE "Episode Number" = 28.0;