please help me on this question

3. Suppose the desired reserve ratio is set at 10% in the banking system. a. What would be the total change in the deposits in the banking system if the central bank sells $2 million government bonds to bank A? Show your calculations! b. What would be the total change in the deposits in the banking system if the central bank buys $1 million government bonds from bank A given that an additional 10% of any deposits are held as excess reserves? Show your calculations