題組內容

4. Let the equilibrium condition for national income be 
S (Y ) + T (Y ) = I (Y ) + G0 (S ',T ', I >  0； S ' + T' > I '), where S , Y , T , I and G stand for saving, national income, taxes, investment, and government expenditure, respectively. All derivatives are continuous.

(a) Check whether the conditions of the implicit-function theorem are satisfied. If so, write the equilibrium identity.