What is the change in net working capital

Question

Problem:

2010 and 2011 Balance Sheets for Nabors, Inc
($ millions)

2010    2011    2010    2011
Cash    $310    $405    Accounts Payable $2,720    $2,570
Accounts Rec.    2640    3,055    Notes Payable    100    0
Inventory    3275    3,850    Long-Term Debt    7,875    8,100
Net Fixed Assets    10,960 10,670    Common Stock    5,000    5,250
Retained Earnings    1,490    2,060
Total Assets    $17,185 $17,980    Total Liab. & Equity $17,185 $17,980

Question: What is the change in net working capital from 2010 to 2011?