Please explain periodic

Practice Question 22 Kam Company has the following units and costs: Units Unit Cost Inventory, Jan.18,000$11 Purchase, June 19 13,000 12 Purchase, Nov. 85,000 13 If 9,000 units are on hand at December 31, what is the cost of the ending inventory under LIFO using a periodic inventory system? $99,000 $100,000 O $108,000 $113,000