The aggregate demand of an open economy is given by the after-tax domestic consumption C, the investment I (which depends on the interest rate r), the government spending G and net exports X - M. Given this equation, which of the following increases the multiplier?

AD = C + I + G + X - M = c0+ c1(1 - t)Y + I(r) + G + X - mY

Select one:

a.A rise in the tax rate.

b.A fall in government spending.

c.A fall in the interest rate.

d.A fall in the marginal propensity to import.