please help me answer a, b, and c!

9. The units of an item available for sale during the year were as follows: January 11 Inventory 90 units @ $86 February 27 Purchase 110 units @ $74 November 21 Purchase 85 units @ $80 There are 80 units of the item in the physical end inventory at December 31. The periodic inventory system is used. Determine the inventory cost by (a) the FIFO method, (b) the LIFO method, and (c) the Average Cost method