How would each of the following transactions affect the GDP of the United States?
a. The U.S. government pays $1 billion in salaries for government workers.
b. The U.S. government pays $1 billion to Social Security recipients.
c. The U.S. government pays a U.S. firm $1 billion for newly produced airplane parts.
d. The U.S. government pays $1 billion in interest to holders of U.S. government bonds.
e. The U.S. government pays $1 billion to Saudi Arabia for crude oil to add to U.S. government-owned oil reserves.