define profitability index The capitalist mode of production first developed from industry and gained dominance, then gradually expanded to agriculture. Because there are two kinds of monopoly in the agriculture, the monopoly capitalism and operation of land and land ownership of monopoly, so it does not have such as like the sort of free competition in the industry, thus hindering the average profit margin. Therefore, the excess profit in agriculture is converted into rent. First, the individual production price of land products is lower than the social production price. The second is absolute rent from the value of land products beyond the price of social production. Both rent entity, agricultural employment is part of the surplus value created by laborer, it embodies the land owners through agricultural capitalist production relations of common exploitation agricultural workers. On the surface, however, the rent is distorted as the value of the land itself, or the gift of nature, thus disguising the real class relationship completely. Under the theoretical framework of the theory, the theory of commodity market equilibrium and the monetary market equilibrium of Keynesian theory are unified. Marx's theory of interest rate decisions from the perspective of the source and essence of interest, taking into account the institutional factors in the role of interest rate decisions of interest theory, its theoretical core is the interest rate is determined by the average profit margin. Marx believed that under capitalism, interest is a part of profit and a form of conversion of surplus value. Commenting on the recent renovations, Ms Stephens said: “I am absolutely delighted with the work that has been carried out and Dortech’s customer service and professional installation has been second to none.