DSE 2008 Question 50: IS-LM model

Setup, from Q47 of the paper:

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:

(Same model.) Suppose we now allow the general price level to be flexible. Given the above characteristics, the aggregate demand curve (output demanded as a function of the general price level) is