U.S had current assets of $1403. at the end of 2009, current assets were $1112, so during the year U.S invested $1403 - 1112 = $291 in current assets.
As the firm changes its investment in current assets, its current liabilities will usually change as well. To determine the change in net working capital, the easiest approach is just to take the difference between the beginning and ending net working capital figures. Net working capital at the end of 2010 was $1112 - 428 =$684. so given these figures, we have: