user: Question: If the call sign is W291CH what's the ERP W corresponding to that sign?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'Class', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['W291CH', 106.1, 'Pittsfield, Massachusetts', 10.0, 'D', 'FCC']
SQL:

assistant: SELECT "ERP W" FROM "Table" WHERE "Call sign" = 'W291CH';