CREATE TABLE table_73976 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( millions ) " TEXT)

Who wrote episode number 109 in the series?
SELECT "Written by" FROM table_73976 WHERE "No. in series" = '109'
SELECT "Written by" FROM "table_73976" WHERE "No. in series" = '109'