pls help

Kiner Co. uses a PERIODIC system and has the following data related to an item of inventory: Inventory, March 1 100 units @ $4.20 Purchase, March 7 350 units @ $4.40 Purchase, March 16 70 units @ $4.50 Sales March 21 390 units Inventory, March 31 ? Show all computations. Compute the cost of ending inventory and COGS using: a) FIFO b) LIFO c) Average cost