user: ### NOW ANSWER:
Question: Which population has a GDP (nominal) of $6.4 billion?
Columns: ['Country', 'Population', 'Area (km²)', 'GDP (nominal)', 'GDP per capita (nominal)']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Kazakhstan', '16,967,000', '2,724,900', '$196.4 billion', '$11,772']
SQL:

assistant: SELECT "Population" FROM "Table" WHERE "GDP (nominal)" = '$6.4 billion';