help understanding missing values

Periodic inventory by three methods; cost of goods sold The units of an item avaitable for sale daring the year were as follows: There are 80 units of the item in the physical inventory at December 31 . The periodic inventory systern is used. Determine the ending inventory cost and the cost of goods sold by three methods, In your calculations round average unit cost to the nearest cent, and round all othe calculations and your final answers to the nearest dollar