Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at the store. An Invoice should include four pieces of information as instance variables— a part number (type string), a part description (type string), a quantity of the item being purchased (type int) and a price per item (decimal). Your class should have a constructor that initializes the four instance variables. Provide a property with a get and set accessor for each instance variable. In addition, provide a method named GetInvoiceAmount that calculates the invoice amount (i.e., multiplies the quantity by the price per item), then returns the amount as a decimal value. If the quantity is negative, it should be left unchanged. Similarly, if the price per item is negative, it should be left unchanged. Write a test application named InvoiceTest that demonstrates class Invoice’s capabilities.