Case 18-1 Hands-on practice in database design is important. Use a relational DBMS to implement the integrated REA data model presented in this chapter, or one of the integrated data models from the homework problems, or a model provided by your instructor. Then, perform the following tasks: 1. Write a query to calculate total accounts receivable. 2. Write a query to calculate accounts receivable for a specific customer. 3. Create a sales invoice form that references the appropriate tables and inputs data about attributes into the proper tables. 4. Write queries to calculate as many financial statement items as possible from the data model you implement. 5. Design appropriate input controls to ensure the validity of data entered in the form created in step 3.