It's not possible to know how much the retailer spent based on the information provided. The information provided only tells us how the retailer selected a sample of receipts from the past week by numbering all the receipts, generating 25 random numbers, and sampling the receipts that correspond to those numbers. In order to know how much the retailer spent, you would need more information such as the total amount of money spent on all the receipts and the amount of money spent on each receipt.