In the following cases, use a periodic inventory system to identify the item(s) designated by the letters

Question:

In the following cases, use a periodic inventory system to identify the item(s) designated by the letters X and Y.
(a) Purchases – X – Y = Net purchases.
(b) Cost of goods purchased – Net purchases + X.
(c) Beginning inventory + X = Cost of goods available for sale.
(d) Cost of goods available for sale – Cost of goods sold = X.