Julia has been thinking about how she uses credit cards. She has two bank cards and three store cards. The APRs on the cards range from 10.5 to 24.9 percent, with the store cards being among the highest. She uses the cards often and picks whatever card she comes to first in her wallet. Most months she pays the balance off in full. However, sometimes she is unable to pay the balance on one or more of the cards, and so she only pays the minimum balance. Julia feels she is doing her best on managing her cards but wants to do better. She is thinking about using just one of her bank cards for any purchases that she thinks she will be unable to pay at the end of the month. Offer your opinions about her thinking.