How many years are left in the lives of Petrobras's "equipment and other assets" on average? State clearly any assumptions that you make in arriving at your estimate.

Marketable securities 10 4,066,280 3,922,370 Project financing 11.2 Deposits in court 12 1,853,092 1,693,495 Prepaid expenses 1,400,072 1,514,301 Advance for pension plan 21 1,296,810 Deferred income and social contribution taxes 20.3 10,238,308 8,333,490 Inventories 8 303,929 236,753 Other long-term receivables 1,256,96 1,325,865 21,254,843 22,022,837 Investments 13 5,106,495 7,822,074 Property, plant, and equipment 14 190,754,167 139,940,726 Intangible assets 15 8,003,213 5,532,053 Deferred charges 3,469,846 2,536,344 228,588,564 177,854,034 292,163,842 231,227,800 See the accompanying notes to the financial statements. Property, Plant, and Equipment By Type of Asset Consolidated 2008 2007 Estimated Useful Accumulated Life in Years Cost Depreciation Net Net Buildings and improvements 25 to 40 9,382,619 (3,115,564) 6,267,055 3,800,350 Equipment and other assets 3 to 30 119,999,208 (55,854,051) 64,145,157 49,414,524 Land 1,138,720 1,138,720 854,848 Material 6,034,143 6,034,143 4,247,098 Advances to suppliers 5,189,735 5,189,735 2,624,093 Expansion projects 59,238,898 59,238,898 39,964,366 Oil and gas exploration and production development costs (E&P) 83,883,258 (35,142,799) 48,740,459 39,035,447 284,866,581 (94,112,414) 190,754,167 139,940,726