the environmental liability includes costs for remediation and restoration of sites , as well as for ongoing monitoring costs , but excludes any anticipated recoveries from third parties . cost estimates are based on information available for each site , financial viability of other potentially responsible parties , and existing technology , laws , and regulations . we believe that we have adequately accrued for our ultimate share of costs at sites subject to joint and several liability . however , the ultimate liability for remediation is difficult to determine because of the number of potentially responsible parties involved , site-specific cost sharing arrangements with other potentially responsible parties , the degree of contamination by various wastes , the scarcity and quality of volumetric data related to many of the sites , and the speculative nature of remediation costs . estimates may also vary due to changes in federal , state , and local laws governing environmental remediation . we do not expect current obligations to have a material adverse effect on our results of operations or financial condition . guarantees 2013 at december 31 , 2006 , we were contingently liable for $ 464 million in guarantees . we have recorded a liability of $ 6 million for the fair value of these obligations as of december 31 , 2006 . we entered into these contingent guarantees in the normal course of business , and they include guaranteed obligations related to our headquarters building , equipment financings , and affiliated operations . the final guarantee expires in 2022 . we are not aware of any existing event of default that would require us to satisfy these guarantees . we do not expect that these guarantees will have a material adverse effect on our consolidated financial condition , results of operations , or liquidity . indemnities 2013 our maximum potential exposure under indemnification arrangements , including certain tax indemnifications , can range from a specified dollar amount to an unlimited amount , depending on the nature of the transactions and the agreements . due to uncertainty as to whether claims will be made or how they will be resolved , we cannot reasonably determine the probability of an adverse claim or reasonably estimate any adverse liability or the total maximum exposure under these indemnification arrangements . we do not have any reason to believe that we will be required to make any material payments under these indemnity provisions . income taxes 2013 as previously reported in our form 10-q for the quarter ended september 30 , 2005 , the irs has completed its examinations and issued notices of deficiency for tax years 1995 through 2002 . among their proposed adjustments is the disallowance of tax deductions claimed in connection with certain donations of property . in the fourth quarter of 2005 , the irs national office issued a technical advice memorandum which left unresolved whether the deductions were proper , pending further factual development . we continue to dispute the donation issue , as well as many of the other proposed adjustments , and will contest the associated tax deficiencies through the irs appeals process , and , if necessary , litigation . in addition , the irs is examining the corporation 2019s federal income tax returns for tax years 2003 and 2004 and should complete their exam in 2007 . we do not expect that the ultimate resolution of these examinations will have a material adverse effect on our consolidated financial statements . 11 . other income other income included the following for the years ended december 31 : millions of dollars 2006 2005 2004 .

2006: rental income: 83
net gain on non-operating asset dispositions: 72
interest income: 29
sale of receivables fees: -33
non-operating environmental costs and other: -33
total: 118
2005: rental income: 59
net gain on non-operating asset dispositions: 135
interest income: 17
sale of receivables fees: -23
non-operating environmental costs and other: -43
total: 145
2004: rental income: 55
net gain on non-operating asset dispositions: 69
interest income: 10
sale of receivables fees: -11
non-operating environmental costs and other: -35
total: 88

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Questions:
what was the change in the rental income from 2005 to 2006?
and what was that rental income in 2005?
how much, then, does that change represent in relation to this 2005 rental income, in percentage?

Answers:
24
59
40.7%