DSE 2008 Question 47: IS-LM model

Consider a closed economy with $\overline{P}$ fixed: $Y=C+I+G$, $C=c(Y-T)$ with $0<c<1$, $I=\overline{I}-dr$ ($d>0$), $T=\tau Y$ ($0<\tau<1$), $G=\overline{G}$, money market $\overline{M}/\overline{P}=L=aY-bi$ ($a,b>0$), and $i=r+\pi^{e}$. In ceteris paribus, a unit increase in government expenditure has the following impact on equilibrium income: