Consider a Simple Macro Model with Demand-Determined Output

Consider a simple macro model with demand-determined output.Using such a model,if economists want to estimate the effect of a given change in desired investment on equilibrium national income,they would multiply the change in desired investment by the reciprocal of one minus

A) the average propensity to save.
B) the marginal propensity to save.
C) the equilibrium level of national income.
D) the marginal propensity not to spend.
E) the marginal propensity to spend.