What is the Community Band with a 4BCB Callsign?
CREATE TABLE "defunct_callsigns" (
  "callsign" text,
  "area_served" text,
  "band" text,
  "freq_currently" text,
  "purpose" text
);
SELECT "band" FROM "defunct_callsigns" WHERE "purpose"='community' AND "callsign"='4bcb';