Personally i feel like the US gov should give a proper apology to those who suffered from slavery and should stop the racial discrimination of people in color.
Here is the formula to calculate GDP:
GDP<span> = C + G + I + NX
</span>Where I is the investment that include all form of capital expenditure
Both sales mentioned above could be considered as a form of Capital expenditure, so the total contribution to GRP would be:
$30 + $ 15 = $ 45
Sign language is your answer i think
Behaviorists probably. They believe external factors change the way we respond to stimuli.