What is the Frequency of Gosford when the Callsign of 2cfm?
CREATE TABLE "defunct_callsigns" (
  "callsign" text,
  "area_served" text,
  "frequency" text,
  "band" text,
  "on_air_id" text,
  "purpose" text
);
SELECT "frequency" FROM "defunct_callsigns" WHERE "area_served"='gosford' AND "callsign"='2cfm';