Econ.Help: The level on national income when we have MPS and Investment !!!?

Question

1- MPS = 1/4 and Investment is reduced by $4 billion. Calculate the reduction in the level of national income.

2- MPC = 1/2, the government decides to increase the taxes by $14 billion and decrease the government expenditures by $13 billion. Calculate the effect on the equillibrium level of national income.

3- $8 billion decrease in government expenditures results in a reduction in equillibrium level of national income by $48 billion. Calculate the multiplier, mpc, and mps

4- mpc = 2/3, increase in investment expenditures by $10 million, increase in government expenditures by $15 million, decreased the level of taxes by 9 million. calculate the level change in national income.

Please economists I need your help again!!

Answer 1

1.

ΔY/ΔI=1/(1-1/4)=4/3

ΔI = -4

ΔY= -4*4/3 = -16/3 = -5.33 billions

2.

ΔY/ΔT= -MPC/(1-MPC)= -0.5/(1-0.5)= -1

ΔT=+14

ΔY=14 * -1= -14

ΔY/ΔG= 1/(1-MPC)=1/(1-0.5) = 2

ΔG = -13

ΔY= -13 * 2 = -26

Total effect = -14 + (-26) = $ - 40 billions

3.

ΔY/ΔG= 1/(1-MPC)

ΔG= -8

ΔY= -48

ΔY/ΔG= -48/ -8 = 6

1/(1-MPC)=6

1-MPC=1/6

MPC=1-1/6=5/6 =0.83

MPS=1-MPC=1-5/6=1/6=0.17

4:

ΔY/ΔI=3

ΔY/ΔG=3

ΔY/ΔT= -2

ΔI=+10

ΔG=+15

ΔT= -9

ΔY(I)=10*3=+30

ΔY(G)=15*3=+30

ΔY(T)= -9 * -2 = +18

Total effect = 30+30+18=$+78 billions