Consider the following system of (three) equations.

Y=C+I+G

C=C(YT)

I=I(Y,i)

This is a simple model for a closed economy with some general functional forms.

Yis GDP,

Tis net taxes,

Cis private consumption,

YTis the disposable income for the private sector,

Iis investments,

iis the interest rate, and

Gis public consumption.

Assume that

(YT)C(YT)CYT(0,1)

iI(Y,i)Ii<0

YI(Y,i)IY>0

IY+CYT<1

Finally, assume that,

G,and

Tand

iare policy variables being determined exogenously by the government and the central bank, respectively.

Which of the total derivatives is incorrect?

a. dC=CYTdYCYTdT

b. dY=dC+dI+dG

c. dI=IYdYIidi