In an interest rate swap, only the net payment is made. In this case,

- the customer pays the bank 4%*(3/12)*$100m

- the bank owes the customer (2% + 100bp))*(3/12)*$100m

Therefore the customer pays (4% - (2% + 100bp))*(3/12)*$100m. 3/12 represents the 3 month time interval. This is equal to a net payment of $250k from the customer to the bank. Therefore Choice 'c' is the correct answer and the rest are incorrect.