Final answer:
Susan would not incur any interest if she paid off her credit card balance within the one-month grace period provided by most credit cards.
Step-by-step explanation:
If Susan had no previous balance on her credit card, and she paid off the balance within one month, she would not have to pay any interest. This is because most credit cards offer a grace period in which you can repay the borrowed amount without incurring interest. It's crucial to understand that carrying a balance from month to month results in interest charges, which are calculated by multiplying your balance by the interest rate. Therefore, by paying off the entire balance before the due date, Susan avoids these additional costs.