Please answer the given financial question based on the context.
Context: table of contents valero energy corporation notes to consolidated financial statements ( continued ) 11 . equity share activity activity in the number of shares of common stock and treasury stock was as follows ( in millions ) : common treasury .
||commonstock|treasurystock|
|balance as of december 31 2015|673|-200 ( 200 )|
|transactions in connection withstock-based compensation plans|2014|1|
|stock purchases under purchase program|2014|-23 ( 23 )|
|balance as of december 31 2016|673|-222 ( 222 )|
|transactions in connection withstock-based compensation plans|2014|1|
|stock purchases under purchase programs|2014|-19 ( 19 )|
|balance as of december 31 2017|673|-240 ( 240 )|
|stock purchases under purchase programs|2014|-16 ( 16 )|
|balance as of december 31 2018|673|-256 ( 256 )|
preferred stock we have 20 million shares of preferred stock authorized with a par value of $ 0.01 per share . no shares of preferred stock were outstanding as of december 31 , 2018 or 2017 . treasury stock we purchase shares of our common stock as authorized under our common stock purchase program ( described below ) and to meet our obligations under employee stock-based compensation plans . on july 13 , 2015 , our board of directors authorized us to purchase $ 2.5 billion of our outstanding common stock with no expiration date , and we completed that program during 2017 . on september 21 , 2016 , our board of directors authorized our purchase of up to an additional $ 2.5 billion with no expiration date , and we completed that program during 2018 . on january 23 , 2018 , our board of directors authorized our purchase of up to an additional $ 2.5 billion ( the 2018 program ) with no expiration date . during the years ended december 31 , 2018 , 2017 , and 2016 , we purchased $ 1.5 billion , $ 1.3 billion , and $ 1.3 billion , respectively , of our common stock under our programs . as of december 31 , 2018 , we have approval under the 2018 program to purchase approximately $ 2.2 billion of our common stock . common stock dividends on january 24 , 2019 , our board of directors declared a quarterly cash dividend of $ 0.90 per common share payable on march 5 , 2019 to holders of record at the close of business on february 13 , 2019 . valero energy partners lp units on september 16 , 2016 , vlp entered into an equity distribution agreement pursuant to which vlp offered and sold from time to time their common units having an aggregate offering price of up to $ 350 million based on amounts , at prices , and on terms determined by market conditions and other factors at the time of .
Question: if the same amount was spent monthly for 24 months purchasing $ 2.5 billion of common stock , what was the monthly average spent be , in billions?
Answer:
0.10417