 Up to now it was sufficient to describe only monetary variables.In order to expand the analysis to compute for instance the value of constant capital "c", variable capital "v" und surplus value (or profit) "s" for the economy as whole or to compute the ratios between these magnitudes like rate of surplus value "s"/"v" or value composition of capital, it is necessary to know the relative size of one department with respect to the other.If both departments I (investment goods) and II (consumption goods) are to grow continuously in equilibrium there must be a certain proportion of size between these two departments.