CREATE TABLE table_73267 ("Gas name" TEXT, "Chemical formula" TEXT, "Lifetime  ( years ) " TEXT, "20-yr" TEXT, "100-yr" TEXT, "500-yr" TEXT)

What is the 500 year where 20 year is 289?
SELECT "500-yr" FROM table_73267 WHERE "20-yr" = '289'
SELECT "500-yr" FROM "table_73267" WHERE "20-yr" = '289'