We use the following terminology in this part: aggregate income Y and disposable income Yd (= Y T), consumption function C(Yd), planned investment function I(r), government spending G, and taxation T = tY where t is the marginal tax rate; r% denotes the real interest rate in the economy. (Note, r is in percentage points, e.g. r = 2 means the interest rate is 2%. When doing calculations, the interest rate should not simply be inserted in decimal form. For example, if r = 2 then I(2) = 124 2 = 122.)

Consider a hypothetical economy where:

• C(Yd)=12+0.75(Y T)
• I(r)=1241r
• G = 120
• t = 20%

1. Using the information above, write out the planned Aggregate Expenditure equa- tion. (Hint: Remember that this takes the form of AE = . . . .)
2. Write down an expression for the Investment-Savings (IS) Curve. (Hint: First use the AE equation to find an expression for equilibrium Y . Next, remember that the IS equation takes the form of r = ....)
3. Assume that inflation is zero, so that i = r. This economy's central bank follows a given Monetary Policy Rule: r = i = 0.025Y +0.0003P , where P is the price level. Given this and the expression for the IS Curve, write down an expression for the Aggregate Demand Curve. (Hint: Remember that the AD Curve takes the form P = . . . .)