Explain fully why, in the calculation of GNP, the sale of I final goods is included while the sale of intermediate goods is excluded.

GNP is the total value of all goods and services produced by a country's residents during a specific period of time, usually a year. It represents the market value of all finished products and services created within an economy, regardless of where the production takes place. GNP is used as an economic indicator to measure the growth and wealth of a country.

Final goods are products and services that have been purchased by their end users, meaning that they will not be used in the production of other goods and services. Examples of final goods include a meal at a restaurant, a bike purchased by a consumer, or even a new computer. Final goods are the ultimate output of production processes, and their consumption or investment leads to satisfaction of consumer needs and growth of the economy.

Intermediate goods are goods that have been produced but will be used as inputs in the production of other goods and services. These products are not counted as final output since they have not reached their final consumers yet. Examples of intermediate goods include raw materials, such as steel or cotton, and semi-finished products, such as electronic components for smartphones or car parts.

In the calculation of GNP, final goods are included because they represent the total value of all goods and services produced by a country's residents during a specific period. Including final goods in GNP allows economists to measure the growth and wealth of a country, as well as to compare the economic performance of different countries.

Intermediate goods are excluded from GNP calculation to avoid double counting. Since intermediate goods are used to produce final goods, their value is already embedded in the price of the final goods they helped produce. If we were to include both intermediate and final goods in GNP calculation, the same value would be counted twice – once for the intermediate good and once for the final good – resulting in an overestimation of the country's overall economic output. In summary, the sale of final goods is included in GNP calculation because they represent the total value of goods and services produced by a country's residents. On the other hand, the sale of intermediate goods is excluded to avoid double counting, as their value is already incorporated in the price of the final goods they are used to produce.