CREATE TABLE table_30369 ("No. in series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT)

What's the production code of the episode originally aired on February 21, 1985?
SELECT MIN("Production code") FROM table_30369 WHERE "Original air date" = 'February 21, 1985'
SELECT MIN("Production code") FROM "table_30369" WHERE "Original air date" = 'February 21, 1985'