Suppose thata country's economic consumption function is given by

C = (10√I + 0.7√I^3 - 0.2I) / (√I)

where C and I are expressed in billion dollars.

a. Find the marginal propensity to save when income is 25 billion dollars.

b. determine the relative rate of change of C with respect to I when income is 25 billion dollars.

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