How many millions of US viewers watched the episode written by Jack Sanderson?
CREATE TABLE "table1_27462177_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "u_s_viewers_millions" text,
  "original_u_s_air_date" text,
  "prod_code" real
);
SELECT "u_s_viewers_millions" FROM "table1_27462177_1" WHERE "written_by"='Jack Sanderson';