Explain the difference between saving and investment as defined by a macroeconomist. Which of the following situations represent investment and which represent saving? Explain.

a. Your family takes out a mortgage and buys a new house.

b. You use your $200 paycheck to buy stock in AT&T.

c. Your roommate earns $100 and deposits it in his account at a bank.

d. You borrow $1,000 from a bank to buy a car to use in your pizza delivery business.