I am currently learning AP macroeconomics and am on Module 27 which discusses the Federal Reserve System and monetary policy. I was confused on a lot of it and am stuck on how to calculate money supply when the bank is expected to keep a certain percentage of required reserves and excess reserves and am confused on how to find the "max" value? For example, I was given this problem on an assignment and am lost

Suppose real GDP is $750 trillion while potential GDP is $1,000 trillion. What open market operation could the central bank use to close the gap? How much would open market operation need to be if the reserve requirement was 10%?