Consider the following description for sales order documents.

“An order document is comprised of several sales orders. Each individual order has a number and it contains the customer information the date when the order was received and item ordered. Each customer has number, name , street, city and zip code. Each item has an item order parts information and quantity. The parts information contains a number, a description of the product and its unit price. The number should treated as attribute when considering XML representation of the document”.

a) Write down appropriate DTD that captures all the information.

b) Create an XML sample instance including one customer and two items.