user: Question: According to W3Counter, what percentage of browsers used Firefox?
Columns: ['Source', 'Chrome', 'Internet Explorer', 'Firefox', 'Safari', 'Opera', 'Other']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['StatCounter', '42.68%', '25.44%', '20.01%', '8.39%', '1.03%', '2.44%']
SQL:

assistant: SELECT "Firefox" FROM "Table" WHERE "Source" = 'W3Counter';