Eli has created $1,000 of gross domestic product. This can be calculated by using the formula of GDP using the income approach.
GDP = Net Income + Indirect Business Taxes + Depreciation
In this problem, we can only compute the Net Income, therefore it would eventually equal to GDP.
To compute the Net Income, you need to subtract all the expenses from the revenue which is $3,500.
$3,500 - $1,200 - $800 - $500 = $1,000