Prepare a DFD that describes the following application: Gadgets, Inc. sells its items through traveling salespeople. When a salesperson receives a signed contract from a client, he or she enters the details into a notebook computer. The salesperson later transmits the record to the company’s mainframe computer at its headquarters. The program records the details in four files: sales, shipping, accounts receivable, and commissions. If the buyer is a new customer (one who is not yet in the customer database), the program enters the customer’s record into the customer database and generates a thank-you letter. The program also calculates the 4 percent commission, which is recorded in the commission file with the salesperson’s code. At the end of the month, the program produces a paper report with the records of all the new customers. In addition, if the total monthly sales of the salesperson exceed 300,000, the program generates a congratulatory letter showing that total. If the total is less than 10,000, the program produces a letter showing the total and the sentence: “Try harder next month.”