Assume the government imposes a $3 tax on buyers, which results in a shift of the demand curve from D1 to D2. The government's tax revenue is

$20 million are added to 2006's GDP with $16 million as consumption and $4 million as private investment

Explanation:

GDP is the total monetary of good and services produced in a country in a given year.

Y=C+I+G+(x-m)

For the question we're told that during 2006 a leading auto manufacturer produced $20 million worth of mini-vans so Y=$20

So out of the $20 total production, $16 million worth of mini-vans were sold which falls under consumption C=$16

And $4 remained unsold out of the total $20 that was produced in 2006. Therefore, I=$4