CREATE TABLE table_203_296 (id DECIMAL, "country" TEXT, "total gdp  ( nominal ) \ ( billion us$ ) " TEXT, "gdp per capita\ ( us$ ,  ppp ) " TEXT, "gdp growth , \ 2007-2011\ ( in % ) " DECIMAL, "hdi" TEXT)

which is the top african nation that earns the most gdp in billions ?
SELECT "country" FROM table_203_296 ORDER BY "total gdp (nominal)\n(billion us$)" DESC LIMIT 1
SELECT "country" FROM "table_203_296" ORDER BY "total gdp (nominal)\n(billion us$)" DESC NULLS LAST LIMIT 1