CREATE TABLE table_28195898_1 (production_code VARCHAR, us_viewers__millions_ VARCHAR)

What is the production code for the episode with 5.5 million u.s. viewers?
SELECT production_code FROM table_28195898_1 WHERE us_viewers__millions_ = "5.5"
SELECT "production_code" FROM "table_28195898_1" WHERE "5.5" = "us_viewers__millions_"