What is a straight-out definition of "vertical economy?

The best definition for GDP is:?

• a.) The sum of the physical amounts of goods and services in the economy. b.) dollar measure of output produced during a given time period. c.) A measure of the per capita economic growth rate of the economy. d.) A physical measure of the capital stock of the economy.

• Answer:

  the answer is (b) because GDP is - The total value ("dollar measure") of goods produced and services provided (these are the "outputs") in a country during one year (or given time period). So therefore (B) satisfies all these conditions for the definition of GDP. (a) is wrong because GDP doesn't measure the amount of good/services, but rather its VALUE. Also (b) is the best answer because it has the phrase "a given time period"; GDP measures the value of goods/services at A GIVEN TIME PERIOD.