CREATE TABLE table_30158 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production" TEXT, "U.S. viewers  ( in millions ) " TEXT)

How many episodes were written by david j. north & janet tamaro?
SELECT COUNT("Original air date") FROM table_30158 WHERE "Written by" = 'David J. North & Janet Tamaro'
SELECT COUNT("Original air date") FROM "table_30158" WHERE "Written by" = 'David J. North & Janet Tamaro'