(2) Net National Product at factor cost Explanation: Net National Product. at factor cost is also called as national income. Net National Product at factor cost is equal to sum total of value added at factor cost or net domestic product at factor cost and net factor income from abroad. NNP al factor cost = NNP at Market Price -Net. Indirect Tax. National income measures the money value of the flow of output of goods and services produced within an economy over a period of Lime.