CREATE TABLE table_18006 ("No." FLOAT, "#" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT, "U.S. viewers  ( million ) " TEXT)

What is the Original air date for the episode directed by Tricia Brock?
SELECT "Original air date" FROM table_18006 WHERE "Directed by" = 'Tricia Brock'
SELECT "Original air date" FROM "table_18006" WHERE "Directed by" = 'Tricia Brock'