CREATE TABLE table_10935205_1 (production_code INT, us_airdate VARCHAR)

The U.S. airdate of 4 april 2008 had a production code of what?
SELECT MAX(production_code) FROM table_10935205_1 WHERE us_airdate = "4 April 2008"
SELECT MAX("production_code") FROM "table_10935205_1" WHERE "4 April 2008" = "us_airdate"