Answer:
View explanation.
Step-by-step explanation:
The question isn't clear on whether or not you are asking if the mom or if the store is owing money to the credit card company. The store owes the full amount paid. The mom owes nothing. You can look at the images for a more detailed explanation, but it is not really needed.
Images from https://www.creditcardinsider.com/blog/happens-credit-card-bill-make-return/
