Suppose that the marginal propensity to save is $\frac{dS}{dy}=0\mathrm{.}3($in billions of dollars$),$ and that consumption is $$8\mathrm{.}70$ billion when disposable income is $0.$ Find the national consumption function. Round your answer to two decimal places.

$C(y)=0\mathrm{.}70y+8\mathrm{.}70$

$C(y)=0\mathrm{.}3y+8\mathrm{.}70$

$C(y)=0\mathrm{.}70y+8\mathrm{.}40$

$C(y)=0\mathrm{.}3y+8\mathrm{.}40$

$C(y)=8\mathrm{.}74$