Consider an economy described as follows: (Y = C + I + G), (Y = 8,000), (G = 2,500), (T = 2,000), (C = 1,000 + 2/3(Y - T)), (I = 1,200 - 100r).

a) Solve for (r)
b) Calculate (C)
c) Determine (Y)
d) Find (I)