The question below is based on the following equations, which refer to a model of a closed economy without a government sector:

A = C + I
C = 600 + 0.75Y
I = 200

Which of the following statements is/are correct?

a. The value of the multiplier is 0.25.
b. The equilibrium income level is 3,200.
c. If investment increases, the equilibrium level of income will increase.
d. All of the above are correct.
e. None of the above is correct.