Final answer:
The excess reserves of Bank A will increase by $250 after the government purchases bonds from them.
Step-by-step explanation:
To calculate the increase in excess reserves, we need to subtract the required reserves from the total reserves.
In this case, the total reserves are $978 and the required reserves are $432. So, the initial excess reserves are $978 - $432 = $546.
When the government purchases bonds worth $250 from Bank A, the bank's reserves will increase by the same amount.
As a result, the excess reserves will also increase by $250.
Therefore, the excess reserves of Bank A will increase by $250 after the government purchases bonds from them.