This problem is a modified version of PP 3 from chapter 5. There is an error for "CalculateCost" in line 12 and I also recieved 7 warnings. the first warning was for "unused local variable 'cost'. The other 6 were for 'name', 'address', 'city', 'lastName', 'firstName', and 'invoiceID' being passed by reference before being assigned a value and could lead to a null reference exception in runtime. Not sure what to do please help.

Furniture Order A furniture manufacturer makes two types of furniture-chairs and sofas. The price per chair is $350, the price per sofa is $925, and the sales tax rate is 5 %. Write a program to create an invoice form for an order. See Fig. 5.40. After the data on the left side of Fig. 5.40 are entered, the user can display an invoice in a list box by pressing the Process Order button. The user can click on the Clear Order Form button to clear all text boxes and the list box, and can click on the Quit button to exit the program. The invoice number consists of the capitalized first two letters of the customer's last name, followed by the last four digits of the zip code. The customer name is input with the last name first, followed by a comma, a space, and the first name. However, the name is displayed in the invoice in the proper order. The generation of the invoice number and the reordering of the first and last names should be carried out by Function procedures Furniture Order Form Customer name Smith William Last, First) Invoice Number: SM4501 Name: Wi111am Smith Address: 123 Geary Street City: Alameda, CA 94501 Address: 123 Street City, State, Zip: Alameda, CA 94501 Number of Chaira: Number of Sofas:9 Number of chairs ordered Price: $9, 725.00 Sales Tax: $486.25 Number of sofas ordered Total Price: $10,211.25 Process Order Clear Order Fornm Quit FIGURE 5.40 Possible outcome of Programming Project 3 Step-by-step solution