public static void Assignment6()
{
Invoice invoice = new Invoice() { Customer = "Kirsi Kernel" };
invoice.Items.Add(new InvoiceItem() { Name = "Milk", Price = 1.75, Quantity = 1 });
invoice.Items.Add(new InvoiceItem() { Name = "Beer", Price = 5.25, Quantity = 1 });
invoice.Items.Add(new InvoiceItem() { Name = "Butter", Price = 2.50, Quantity = 2 });
invoice.PrintInvoice();
}