Please help and explain. Thanks

Inventory records for Dunbar Incorporated revealed the following: Date Transaction Apr. 1 Beginning inventory Apr.20 Purchase Number of Units 510 340 Unit Cost $2.47 2.80 Dunbar sold 630 units of inventory during the month. Ending inventory assuming weighted-average cost would be: (Round welghted-average unit cost to 4 decimal places and final answer to the nearest dollar amount.) Multiple Choice $642 $580. $540 $572