user: Question: What's the highest annual interchange for Wimbledon railway station?
Columns: ['Rank', 'Railway Station', 'Annual entry/exit (millions) 2011–12', 'Annual interchanges (millions) 2011–12', 'Total Passengers (millions) 2011–12', 'Location', 'Number of Platforms']
Types: ['real', 'text', 'real', 'real', 'real', 'text', 'real']
Sample row: [1.0, 'London Waterloo', 94.046, 9.489, 103.534, 'London', 19.0]
SQL:

assistant: SELECT "Annual interchanges (millions) 2011–12" FROM "Table" WHERE "Railway Station" = 'Wimbledon';