Exercise 9-18 (Algo) Retail inventory method; solving for unknowns [LO9-3] Aztec Corporation uses a periodic inventory system and the retail inventory method to estimate ending inventory and cost of goods sold. The following data are available for the month of September: Cost Retail Beginning inventory $ 26,000 $ 39,000 Net purchases 13,000 ?question mark Net markups 8,300 Net markdowns 2,300 Net sales ?question mark The company used the average cost flow method and estimated inventory at the end of September to be $22,980.00. If the company had used the LIFO cost flow method, the cost-to-retail percentage would have been 50%