Assume the following model of the economy, with the prices level fixed at.

The consumption function is given by C=10+0.5(Y-T)

The investment function is 1=10-20r

Government purchases and taxes are both 50.

The money demand function is (M/P) = Y-5r

The money supply is 80.

4.1. Write numerical formula for the IS curve, showing Y as a function of r alone

4.2. Write numerical formula for the LM curve, showing Y as a function of r alone

4.3. Find equilibrium interest rate r and the equilibrium level of income Y

4.4. Without any calculation, explain what could be the impact of increasing government expenditure on the interest rate? (Given a detailed explanation to get full points)