CREATE TABLE table_28422 ("No." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. viewers  ( million ) " TEXT, "Rank  ( week ) " FLOAT, "Original air date" TEXT, "Production code" TEXT)

What is the weeks rank for the episode with the production code 1alf05?
SELECT MAX("Rank (week)") FROM table_28422 WHERE "Production code" = '1ALF05'
SELECT MAX("Rank (week)") FROM "table_28422" WHERE "Production code" = '1ALF05'