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

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'