Help me with these three problems, please!!

1. FIFO and LIFO costs under perpetual inventory system. The following units of an item were available for sale during the year.

2. Periodic Inventory by Three Methods. The units of an item available for sale during the year were as follows:

3. Periodic inventory by three methods; cost of goods sold. The units of an item available for sale during the year were as follows:

Periodic inventory by three methods; cost of goods sold The units of an item available for sale during the year were as follows: There are 80 units of the item in the physical inventory at December 31 . The periodic inventory system is used