When 5a06 is the production code what is the highest episode?
CREATE TABLE "table1_20967430_3" (
  "ep" real,
  "season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "prod_code" text
);
SELECT MAX("ep") FROM "table1_20967430_3" WHERE "prod_code"='5A06';