Which Rank is the lowest one that has a Borough of richmondshire, and a Population larger than 8,178?
CREATE TABLE "settlements_by_population" (
  "rank" real,
  "town" text,
  "population" real,
  "year" real,
  "borough" text,
  "definition" text
);
SELECT MIN("rank") FROM "settlements_by_population" WHERE "borough"='richmondshire' AND "population">'8,178';