What was the gdp of the country with a gdp per capita of $18048?
create table table_1307842_6 (gdp__billion_us$_ varchar, gdp_per_capita__us$_ varchar, PRIMARY KEY (gdp__billion_us$_))
select gdp__billion_us$_ from table_1307842_6 where gdp_per_capita__us$_ = 18048