Final answer:
The GDP is $500 which is the value of the final goods produced including trees, lumber, and bookshelves.
Step-by-step explanation:
The GDP, or Gross Domestic Product, measures the total value of all final goods and services produced within a country during a specific period of time. To calculate the GDP, we need to consider the value of the final goods produced, which includes the value of the trees, lumber, and bookshelves in this case.
Based on the information provided, the nation's GDP would be $500, which is the value of the final goods produced, namely the bookshelves. This includes the value of the trees that were cut down, the lumber produced, and the bookshelves manufactured.