What effect does each of the following have on the U.S. monetary base?

What effect does each of the following have on the U.S. monetary base?

What effect does each of the following have on the U.S. monetary base?
a. The Fed purchases $10 billion of foreign assets.
b. The Fed sells $10 billion of foreign assets and purchases $10 billion of Treasury securities.
c. The Fed conducts a sterilized foreign exchange intervention.
d. The Fed sells $10 billion of foreign assets and sells $10 billion of Treasury securities.
What effect does each of the following have on the U.S. monetary base?