Develop an activity diagram based on the following narrative. Note any ambiguities

that you have as you develop the model. If you need to make assumptions, also note

them.

When a contractor buys materials at Quality Building Supply, he takes it to the contractor

checkout desk. The clerk enters the contractor name into a point of sale system $($the system$)$

as he$/$she provided. The system displays the contractor record, including his current credit

standing. The clerk then opens up a new sales record for the contractor. Next, the clerk scans

in the number of the item to be purchased into the system. The system finds the price and

product name, then displays these on the screen and adds the item to the sales record. In turn,

the clerk enters the quantity of the item.

When all items are scanned, the clerk ends the sale. The system calculates the total and prints

a receipt.