Write the next sentence in the following story.

How to write a letter to reduce credit card interest rates
Create a file that includes other offers from credit cards or balance transfer offers with lower interest rates offered.
If you haven't received any in the mail, or if you've thrown them all in the trash, do some research online to find other offers with lower interest rates.
Find out what the current prime rate is.

Available options:
[a]. Some credit cards may offer lower rates because they don't get as many offers. If that's the case, try avoiding investing in credit cards.;
[b]. Rarely are you able to pay interest in a certain range of monthly or monthly interest rates. Your state's department of credit counseling and billing authority can help you in this subject.;
[c]. The federal reserve sets this as a standard for lenders and banks. Credit card companies use this to set their interest rates, usually staying within 9 percent of the prime rate.;
[d]. Find out how the company currently charges for credit cards, and how they finance their store. Then use this information to determine your credit limit.;. The answer should be
[c].