CREATE TABLE table_74175 ("Series #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. viewers  ( million ) " TEXT)

How many episodes had a production code 120?
SELECT COUNT("Series #") FROM table_74175 WHERE "Production code" = '120'
SELECT COUNT("Series #") FROM "table_74175" WHERE "Production code" = '120'