Phillips Supply uses a periodic inventory system but needs to determine the approximate amount of inventory at the end of each month without taking a physical inventory. Phillips has provided the following inventory data. Cost Price Retail Selling Price Inventory of merchandise, June 30 $ 309,000 $ 505,000 Purchases during July 221,000 396,000 Goods available for sale during July $ 530,000 $ 901,000 Net sales during July $ 200,000 a.