National expenditure is aggregate spending on national output .
Natural environment embraces natural resources including land, vegetation, wildlife, air and water and the amenity which they confer. National income is a measure of the value of goods and services available to the people in an economy in a given period. National income is the incomes created from producing the output. National output is sum of the value added by each domestic firm. Natural monopoly is a firm that can satisfy all the market demand, but still has unexploited cost savings.