How many deciles have a Gender of coed, an Authority of state, and a Name of mount maunganui school?
CREATE TABLE "tauranga_city" (
  "name" text,
  "gender" text,
  "area" text,
  "authority" text,
  "decile" real
);
SELECT SUM("decile") FROM "tauranga_city" WHERE "gender"='coed' AND "authority"='state' AND "name"='mount maunganui school';