Answer:
$80
Step-by-step explanation:
GDP is the total market value of final goods and services produced within an economy. The wool sold by Angus to Barnaby is an intermediate goods. We can not take the value of an intermediate good and add to the GDP as it is part of what was used to produce the sweaters.
So two sweaters were produced as final goods, one sold to Collette and the other remains.
The GDP is therefore the value of the two sweaters produced as final good. GDP = 2 × $40 = $80