What is the sum of the numbers in series written by sam meikle, which have 21 numbers in the season?
CREATE TABLE "episodes" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "ratings" text
);
SELECT SUM("no_in_series") FROM "episodes" WHERE "written_by"='sam meikle' AND "no_in_season"=21;