4. Express Corp. shows the following inventory information for the month of April: April 01: Beginning Inventory 200 units @ $4 per unit April 09: Purchased 500 units @ $4.50 per unit April 17: Purchased 400 units @ $4.75 per unit April 30: Purchased 300 units @ $5 per unit Total sales in April were 900 units at a price of $10 per unit. Required: Calculate the Gross Profit under FIFO, LIFO and AVCO method, assuming that the company uses periodic inventory system. (3)