Which episode had bbc ranking and canle ranking of n/a?
CREATE TABLE "table1_24399615_10" (
  "episode_no" real,
  "airdate" text,
  "viewers" text,
  "bbc_three_weekly_ranking" text,
  "cable_rank" text
);
SELECT COUNT("episode_no") FROM "table1_24399615_10" WHERE "bbc_three_weekly_ranking"='N/A' AND "cable_rank"='N/A';