CREATE TABLE table_8766 ("Callsign" TEXT, "Frequency" TEXT, "Band" TEXT, "On-air ID" TEXT, "Purpose" TEXT)

4tab of commercial broadcaster Radio Tab broadcasts at what frequency?
SELECT "Frequency" FROM table_8766 WHERE "Purpose" = 'commercial' AND "On-air ID" = 'radio tab' AND "Callsign" = '4tab'
SELECT "Frequency" FROM "table_8766" WHERE "Callsign" = '4tab' AND "On-air ID" = 'radio tab' AND "Purpose" = 'commercial'