Answer and Explanation:
The journal entries are shown below:
1. Inventory $1,800
    Accounts Payable $1,800
(Being purchased on account)
2. Inventory $50
   To Cash $50
(being freight paid)
3. Accounts Payable $51
   To Inventory $51
(being the returned calculator is recorded)
4. Accounts Receivable $670
    To Sales Revenues $670
(Being sales is recorded)
5. Cost of Goods Sold $460
   To Inventory $460
(Being cost of goods sold is recorded)
6. Â Sales returns $40
     To Accounts Receivable $40
(being sales return is recorded)
7. Inventory $28.20
   To Cost of Goods Sold $28.20
(Being cost return is recorded)
8. Accounts Receivable $780
   To Sales Revenues $780
(Being the sales is recorded)
9. Cost of Goods Sold $560
   To Inventory $560
(Being the cost of goods sold is recorded)