Marginal Propensity to Save Suppose C(x) measures an economy's personal consumption expenditure and x the personal income, both in billions of dollars. Then the following function measures the economy's savings corresponding to an income of x billion dollars:
S(x) = x - C(x) (income minus consumption)
The quantity dS/dx below is called the marginal propensity to save.
dS/dx = 1 - dC/dx
For the following consumption function, find the marginal propensity to save when x = 4. (Round your answer to three decimal places.)
C(x) = 0.888x^1.1 + 23.69
billion per billion dollars