Answer:
$50 million
Step-by-step explanation:
Gross domestic product is the sum of all final goods and services produced in an economy within a given period which is usually a year.
An economy is closed if it doesn't trade with other countries.
GDP = Consumption spending + Investment spending + Government Spending
$750 million = $300 million + Investment spending + $400 million
Investment spending = $50 million
I hope my answer helps you