Final answer:
The cost of the merchandise returned cannot be determined with the information provided as there are no clear indications of which transactions represent returns.
Step-by-step explanation:
From the information provided, it is not clear which transactions represent returns of merchandise. Therefore, with the current data, we cannot establish a direct method to calculate the cost of the merchandise returned. To determine the cost of returned merchandise, one would typically subtract the total sales after returns from the total sales before returns. However, without specific details indicating which of the amounts provided in the list represent the returns, or without an original sales tally to compare against returns, the exact cost of merchandise returned cannot be identified within the options presented: $130, $100, $150, or $200.