VS 2008 - Querying Array Of Invoice Objects (LINQ)

Use the Invoice Class provided to create an array of Invoice Objects. Class Invoice includes four properties- a PartNumber (type integer), a PartDescription (type String), a Quantity of the item being purchased (type Integer), and a Price (type Decimal). Write a Console Application that performs the following queries on the array of Invoice objects and displays the results:

a. Use LINQ to sort the Invoice Objects by PartNumber
b. Use LINQ to sort the Invoice objects by Price
c. Use LINQ to select the PartDescription and Quantity and sort the results by Quantity
d. Use LINQ to select from each Invoice the PartDescrition and the value of the Invoice (i.e. Quantity * Price). Name the calculated column InvoiceTotal. Order the results by InvoiceTotal.
e. Using the results of the LINQ query in Pard d, select the InvoiceTotals in the range of $200 to $500

I am pretty sure I have parts a, b, & c completed correctly. Or at least the provide the desired results. Part d I figured out how to multiply the 2 fields but can't create a new column for the result or figure out how to show the PartDescription with the multiplied result. Part c I think I can figure out when I get part d. I already coded what I think will work for part c.

Below are the 2 Objects the Invoice was given and not to be changed & the LINQ is the one I have been working on.
Module LINQ
Sub Main()
' array of invoices
Dim invoices As Invoice() = { _
New Invoice("83", "Electric Sander", "7", 59.98), _
[Code] .....