82 | 2017 form 10-k a reconciliation of the beginning and ending amount of gross unrecognized tax benefits for uncertain tax positions , including positions impacting only the timing of tax benefits , follows . reconciliation of unrecognized tax benefits:1 years a0ended a0december a031 .

years ended december 31 , 2017: balance at january 1,: 1032
additions for tax positions related to current year: 270
additions for tax positions related to prior years: 20
reductions for tax positions related to prior years: -27
reductions for settlements2: -9
reductions for expiration of statute of limitations: 2014
balance at december 31,: 1286
amount that if recognized would impact the effective tax rate: 1209
years ended december 31 , 2016: balance at january 1,: 968
additions for tax positions related to current year: 73
additions for tax positions related to prior years: 55
reductions for tax positions related to prior years: -36
reductions for settlements2: -24
reductions for expiration of statute of limitations: -4
balance at december 31,: 1032
amount that if recognized would impact the effective tax rate: 963

1 foreign currency impacts are included within each line as applicable . 2 includes cash payment or other reduction of assets to settle liability . we classify interest and penalties on income taxes as a component of the provision for income taxes . we recognized a net provision for interest and penalties of $ 38 million , $ 34 million and $ 20 million during the years ended december 31 , 2017 , 2016 and 2015 , respectively . the total amount of interest and penalties accrued was $ 157 million and $ 120 million as of december a031 , 2017 and 2016 , respectively . on january 31 , 2018 , we received a revenue agent 2019s report from the irs indicating the end of the field examination of our u.s . income tax returns for 2010 to 2012 . in the audits of 2007 to 2012 including the impact of a loss carryback to 2005 , the irs has proposed to tax in the united states profits earned from certain parts transactions by csarl , based on the irs examination team 2019s application of the 201csubstance-over-form 201d or 201cassignment-of-income 201d judicial doctrines . we are vigorously contesting the proposed increases to tax and penalties for these years of approximately $ 2.3 billion . we believe that the relevant transactions complied with applicable tax laws and did not violate judicial doctrines . we have filed u.s . income tax returns on this same basis for years after 2012 . based on the information currently available , we do not anticipate a significant increase or decrease to our unrecognized tax benefits for this matter within the next 12 months . we currently believe the ultimate disposition of this matter will not have a material adverse effect on our consolidated financial position , liquidity or results of operations . with the exception of a loss carryback to 2005 , tax years prior to 2007 are generally no longer subject to u.s . tax assessment . in our major non-u.s . jurisdictions including australia , brazil , china , germany , japan , mexico , switzerland , singapore and the u.k. , tax years are typically subject to examination for three to ten years . due to the uncertainty related to the timing and potential outcome of audits , we cannot estimate the range of reasonably possible change in unrecognized tax benefits in the next 12 months. .

Questions:
in the years of 2017 and 2016, combined, what was the total provision for interest and penalties?
including to that period 2015, what becomes this total?
and what is the average between those three years?
and in the two last years of this period, what was the proportional increase in the total amount of interest and penalties accrued, or how much did the 2017 amount represent in relation to the 2016 one?
assuming this proportional increase continues through 2017 to 2018, what will be, in 2018, that amount of interest and penalties accrued, in millions?

Answers:
72
92
30.7
131%
205.4