user: Question: What is the QS World ranking of the school with the Times ranking 251-275?
Columns: ['University', 'Location', 'Year Founded', 'QS World University Rankings 2012', 'Times Higher Education World University Rankings 2012-2013']
Types: ['text', 'text', 'real', 'real', 'text']
Sample row: ['Nanjing University', 'Nanjing', 1902.0, 168.0, '251-275']
SQL:

assistant: SELECT "QS World University Rankings 2012" FROM "Table" WHERE "Times Higher Education World University Rankings 2012-2013" = '251-275';