CREATE TABLE table_28980706_4 (first_air_date VARCHAR, rating__18_49_ VARCHAR)

When 4.5 is the rating (18-49) what is the air date?
SELECT first_air_date FROM table_28980706_4 WHERE rating__18_49_ = "4.5"
SELECT "first_air_date" FROM "table_28980706_4" WHERE "4.5" = "rating__18_49_"