CREATE TABLE table_1378 ("No. in series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. viewers  ( million ) " TEXT, "Original air date" TEXT, "Production code" FLOAT)

How many episodes were written by Jack Burditt & Robert Carlock
SELECT COUNT("Production code") FROM table_1378 WHERE "Written by" = 'Jack Burditt & Robert Carlock'
SELECT COUNT("Production code") FROM "table_1378" WHERE "Written by" = 'Jack Burditt & Robert Carlock'