{"pre_text": ["in 2017 , the company granted 440076 shares of restricted class a common stock and 7568 shares of restricted stock units .", "restricted common stock and restricted stock units generally have a vesting period of two to four years .", "the fair value related to these grants was $ 58.7 million , which is recognized as compensation expense on an accelerated basis over the vesting period .", "dividends are accrued on restricted class a common stock and restricted stock units and are paid once the restricted stock vests .", "in 2017 , the company also granted 203298 performance shares .", "the fair value related to these grants was $ 25.3 million , which is recognized as compensation expense on an accelerated and straight-lined basis over the vesting period .", "the vesting of these shares is contingent on meeting stated performance or market conditions .", "the following table summarizes restricted stock , restricted stock units , and performance shares activity for 2017 : number of shares weighted average grant date fair value ."], "post_text": ["the total fair value of restricted stock , restricted stock units , and performance shares that vested during 2017 , 2016 and 2015 was $ 66.0 million , $ 59.8 million and $ 43.3 million , respectively .", "under the espp , eligible employees may acquire shares of class a common stock using after-tax payroll deductions made during consecutive offering periods of approximately six months in duration .", "shares are purchased at the end of each offering period at a price of 90% ( 90 % ) of the closing price of the class a common stock as reported on the nasdaq global select market .", "compensation expense is recognized on the dates of purchase for the discount from the closing price .", "in 2017 , 2016 and 2015 , a total of 19936 , 19858 and 19756 shares , respectively , of class a common stock were issued to participating employees .", "these shares are subject to a six-month holding period .", "annual expense of $ 0.3 million for the purchase discount was recognized in 2017 , and $ 0.2 million was recognized in both 2016 and 2015 .", "non-executive directors receive an annual award of class a common stock with a value equal to $ 100000 .", "non-executive directors may also elect to receive some or all of the cash portion of their annual stipend , up to $ 60000 , in shares of stock based on the closing price at the date of distribution .", "as a result , 19736 shares , 26439 shares and 25853 shares of class a common stock were issued to non-executive directors during 2017 , 2016 and 2015 , respectively .", "these shares are not subject to any vesting restrictions .", "expense of $ 2.5 million , $ 2.4 million and $ 2.5 million related to these stock-based payments was recognized for the years ended december 31 , 2017 , 2016 and 2015 , respectively. ."], "table": [["", "number of shares", "weightedaveragegrant datefair value"], ["outstanding at december 31 2016", "1820578", "$ 98"], ["granted", "650942", "129"], ["vested", "-510590 ( 510590 )", "87"], ["cancelled", "-401699 ( 401699 )", "95"], ["outstanding at december 31 2017", "1559231", "116"]], "table_ori": [["", "Number of Shares", "WeightedAverageGrant DateFair Value"], ["Outstanding at December 31, 2016", "1,820,578", "$98"], ["Granted", "650,942", "129"], ["Vested", "(510,590)", "87"], ["Cancelled", "(401,699)", "95"], ["Outstanding at December 31, 2017", "1,559,231", "116"]]}

Question: in millions , how much compensation expense was attributable to directors in the years ended december 31 , 2015 through 2017?
Evidence:
text_19: expense of $ 2.5 million , $ 2.4 million and $ 2.5 million related to these stock-based payments was recognized for the years ended december 31 , 2017 , 2016 and 2015 , respectively. .
Program: add(2.4, 2.5), add(#0, 2.5)
Answer:
str_answer: 7.4
exe_answer: 7.4