KoKo Company uses the retail method of inventory costing. They started the year with an inventory that had a retail cost of $35,000. During the year they purchased an inventory with a retail cost of $300,000. After performing a physical inventory, they calculated their inventory at $60,000. The mark up is 100% of cost. Determine the ending inventory at its estimated cost.

are you looking for the cost price of ending inventory at retail price of 60,000. Then it is as follows:
retail price = 60000
markup = 100
margin = [(markup)/(100+markup)]*100
i.e margin = 50%
cost price of the ending inventroy = 50% of 60000
= 30000