CREATE TABLE table_57421 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT)

What is the highest production code when the writer was brian egeston after season 5?
SELECT MAX("Production code") FROM table_57421 WHERE "Written by" = 'brian egeston' AND "Season #" > '5'
SELECT MAX("Production code") FROM "table_57421" WHERE "Season #" > '5' AND "Written by" = 'brian egeston'