CREATE TABLE table_29682 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. viewers  ( millions ) " TEXT, "Original U.S. air date" TEXT, "Prod. code" TEXT)

which is the production code when the number of the episode in series is 87?
SELECT "Prod. code" FROM table_29682 WHERE "No. in series" = '87'
SELECT "Prod. code" FROM "table_29682" WHERE "No. in series" = '87'