The equilibrium level of real GDP is $\$ 1,000$ billion, the full-employment level of real GDP is $\$ 1,250$ billion, and the marginal propensity to consume (MPC) is $0.60 .$ The full-employment target can be reached if government spending is
a. increased by $\$ 60$ billion.
b. increased by $\$ 100$ billion.
c. increased by $\$ 250$ billion.
d. held constant.