When the call sign is wpib, what is lowest ERP W?
CREATE TABLE table_name_21 (erp_w INTEGER, call_sign VARCHAR)
SELECT MIN(erp_w) FROM table_name_21 WHERE call_sign = "wpib"
### Context: CREATE TABLE table_name_21 (erp_w INTEGER, call_sign VARCHAR) ### Question: When the call sign is wpib, what is lowest ERP W? ### Answer: SELECT MIN(erp_w) FROM table_name_21 WHERE call_sign = "wpib"