 who is the writer where viewers is 5.16m
CREATE TABLE "table1_12148018_2" (
  "num" real,
  "episode" text,
  "director" text,
  "writer" text,
  "original_airdate" text,
  "viewers" text
);
SELECT "writer" FROM "table1_12148018_2" WHERE "viewers"='5.16m';