Draw the DFD (Context and Level-0) for an order processing system that has the following activities:

• Customers place orders by telephone or fax;
• Customer orders are processed to verify that order information is accurate and record exists for the customer placing the order.If a customer record does not exist, it is added to the customer master file.Valid order information is entered in the order master file.As orders are entered, customer and order master files are updated.
• If a customer orders more of an item than is currently available in stock, back-order item information is sent to the inventory control department.
• For the orders that can be shipped immediately, order picking list is prepared and sent to Warehouse.

Please use Gane and Sarson symbols in the DFD.