Answer and Explanation:
The Journal entry is shown below:-
1. Inventory Dr, $1,800
        To accounts payable $1,800
(Being purchase of calculators on account is recorded)
2. Inventory Dr, $50
      To cash $50
(Being inventory is recorded)
3. Accounts payable Dr, $51
      To inventory $51
(Being return of calculators is recorded)
4. Accounts Receivable $670
      To Sales revenue $670
(Being sales revenue is recorded)
5. Cost of Goods Sold Dr, $460
      To Inventory $$460
(Being cost of goods sold is recorded)
6. Sales returns Dr, $40
      To Accounts receivable $40
(Being goods returned by customer is recorded)
7.  Inventory Dr, $28
      To Cost of Goods Sold $28
(Being cost of goods sold returned is recorded)
8. Cost of Goods Sold Dr, $780
       To Sales revenue $780
(Being cost of goods sold is recorded)
9. Cost of Goods Sold Dr, $560
       To inventory $560
(Being cost of goods sold is recorded)