You create an application by using the Microsoft .NET Framework 3.5 and Microsoft ADO.NET. The application connects to a Microsoft SQL Server 2005 database.

The application uses a strongly typed DataTable class named Invoice to process order invoices.
The application contains third-party components and the Invoice DataTable class that cannot be recompiled.
The application processes the order invoices by passing the Invoice DataTable object to these third-party components.

You need to calculate the tax amount for each order invoice in the Invoice DataTable object.

What should you do?

A.
+ Add a partial class named Invoice to the application.
+ Write a method to calculate the tax amount in the partial class.
+ Use the original Invoice typed DataTable object to process order invoices.

B.
+ Modify the generated source code for the Invoice typed DataTable object to contain a method that calculates the tax amount.
+ Update the application to use the new Invoice typed DataTable object to process order invoices.

C.
+ Create a class named TaxableInvoice that inherits from the Invoice class.
+ Write a method to calculate the tax amount in the TaxableInvoice class.
+ Update the application to use the TaxableInvoice typed DataTable object instead of the Invoice DataTable object to process order invoices.

D.
+ Create a utility class named InvoiceTaxCalculator for which the constructor takes an Invoice DataTable object.
+ Write a method to calculate the tax amount in the InvoiceTaxCalculator utility class.
+ Update the application to use the InvoiceTaxCalculator typed DataTable object instead of the Invoice DataTable object to process order invoices.