I'm currently a little confused, thank you for your help!

1. Assume an economy can be modeled with these equations: C = 170 + 0.8 Yd, I = 200, G = 53 - 0.052 Y, X = 320 M = 375 and T = 10 + 0.3Y. What is the multiplier on Taxation (ie if T0 increases by 1, how much does Y increase)? Sign & 2 decimals please.
2. Assume an economy can be modeled with these equations: C = 280 + 0.75 Yd, I = 200, G = 107 - 0.047 Y, X = 300 M = 345 and T = -40 + 0.26Y. What is the new value of Y when Investment rises by 5? 2 decimals please.
3. Assume an economy can be modeled with these equations: C = 270 + b Yd, I = 200, G = 101 - 0.045 Y, X = 330 M = 345 and T = -40 + 0.23Y. What is the value of b when the multiplier on Investment is 0.5368? 2 decimals please.
4. Suppose a US investor has $5100 to invest and can choose either a US investment paying 5.25% or a foreign investment paying Rf%, where e is currently 11.3 and future e is 11.8. What Rf would leave the investor indifferent between investing at home or abroad? Use 2 decimals so if Rf is 12.34% enter 12.34.