Can anyone help me with a Macroeconomics question?

Question

The banking system currently has $50 billion of reserves. People hold only deposits and no currency, and the reserve requirement is 10%. If the Fed raises the reserve requirement to 12.5% and at the same time sells $10 billion of bonds, how much does the money supply change?

Answer 1

At 10% reserves your money supply is $500 billion

At 12.5% reserves your money supply is $400 billion or changed $100 billion

If bonds are sold, money is taken out of the system of $10 billion and take account of reserve - changed 80 billion

So the new money supply changed $180 billion