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**shannon1111** The consumption function is given by

c=((14squar root of I^3)-35)/(I+9)

where *I* is the total national income and *C* the total national consumption, both expressed in billions of dollars.

A)The **marginal propensity to consume** is defined as the rate of change of consumption with respect to income:

Marginal propensity to consume = *dC/dI*

The marginal propensity to consume for the consumption function *C* given above when *I*=81 equals ______(billions of dollars)/(one billion of dollars of change of the income).