CREATE TABLE table_35110 ("Callsign" TEXT, "Area served" TEXT, "Frequency" TEXT, "Band" TEXT, "Freq currently" TEXT, "Purpose" TEXT)

What is the purpose for the katherine freq of 8rn?
SELECT "Purpose" FROM table_35110 WHERE "Freq currently" = '8rn' AND "Area served" = 'katherine'
SELECT "Purpose" FROM "table_35110" WHERE "Area served" = 'katherine' AND "Freq currently" = '8rn'