Sidney took a $600 cash advance by using checks linked to her credit card account. The bank charges a 2 percent cash advance fee on the amount borrowed and offers no grace period on cash advances. Sidney paid the balance in full when the bill arrived.

a) What was the cash advance fee? (Round your answer to 2 decimal places.)

b) What was the interest for one month at an APR of 18 percent? (Round your answer to 2 decimal places.)

c) What was the total amount she paid? (Round your answer to 2 decimal places.)

d) What if she had made the purchase with her credit card and paid off her bill in full promptly? Assume the credit card has a grace period. (Round your answer to 2 decimal places.)