Paraphrase this :

if you don't pay off the balance for a credit card every month, you'll be charged interest on the unpaid balance, making that pizza you charged a lot more expensive.

Every month you have to pay off all the items that are on your credit card, and if you do not follow this simple rule,  you will have to pay interest.  Interest is when you are forced by the government to pay more than the item you bought.  This punishment will continue to happen each month that you choose to not pay off your debts.  Therefore the pizza you bought would become a lot more expensive.

Explanation:

i do not the question is put in the corrorect order

queen elizabeth's purpose in the passage is;

d. to persuade the troops that she is a capable commander

"i have the heart and stomach of a king. i myself will be your general, judge, and rewarder."