user: Question: On what frequency does w233ag broadcast?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'Height m ( ft )', 'Class', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text', 'text', 'text']
Sample row: ['W220CE', 91.9, 'Southington, CT', 1.0, 'm (ft)', 'D', 'FCC']
SQL:

assistant: SELECT "Frequency MHz" FROM "Table" WHERE "Call sign" = 'w233ag';