Assume that a closed economy is characterized by the following in the short run: C =100+3/4(Y-T) I=170-500r G =125T-100 L(r,Y)=2Y-10,000r M=10,000 P =5 a) Use the information to derive the IS and LM equations. b) Use the IS and LM equations to derive the level of Y, r, C, and I in the short run. c) Calculate how an increase in government spending to G=150 (so G increases by 25) affects the level of Y, r, C, and I in the short-run assuming prices are fixed. d) If you wanted to use monetary policy instead of fiscal policy to increase Y by as much as you did in part C (starting from the original equilibrium in part B), what would the real interest rate (r) have to be and by how much would you need to change the money supply?