Consider the short-run model. Suppose the economy starts in a situation where there are no AD shocks (normal-times AD) and the real interest rate is equal to the MPK. Suppose that the government increases its purchases to launch a large infrastructures program. Assuming the Fed keeps the interest rate unchanged, which curve will shift in the IS-MP diagram and how?

a-The MP curve will shift up.

b-The PC curve will shift up.

c-The IS curve will shift to the left.

d-The IS curve will shift to the right.