What is the roll number of the school with a state authority in Waiotira?
CREATE TABLE "whangarei" (
  "name" text,
  "years" text,
  "area" text,
  "authority" text,
  "decile" text,
  "roll" text
);
SELECT "roll" FROM "whangarei" WHERE "authority"='state' AND "area"='waiotira';