Calculate U.S. net investment and gross investment during 2018.

The Bureau of Economic Analysis reported that the U.S. capital stock was $64.8 trillion at the end of 2017, $68.2 trillion at the end of 2018, and $70.7 trillion at the end of 2019. Depreciation in 2018 was $3.3 trillion, and gross investment during 2019 was $3.8 trillion.