{"pre_text": ["other information related to the company's share options is as follows ( in millions ) : ."], "post_text": ["unamortized deferred compensation expense , which includes both options and rsus , amounted to $ 378 million as of december 31 , 2015 , with a remaining weighted-average amortization period of approximately 2.1 years .", "employee share purchase plan united states the company has an employee share purchase plan that provides for the purchase of a maximum of 7.5 million shares of the company's ordinary shares by eligible u.s .", "employees .", "the company's ordinary shares were purchased at 6-month intervals at 85% ( 85 % ) of the lower of the fair market value of the ordinary shares on the first or last day of each 6-month period .", "in 2015 , 2014 , and 2013 , 411636 shares , 439000 shares and 556000 shares , respectively , were issued to employees under the plan .", "compensation expense recognized was $ 9 million in 2015 , $ 7 million in 2014 , and $ 6 million in 2013 .", "united kingdom the company also has an employee share purchase plan for eligible u.k .", "employees that provides for the purchase of shares after a 3-year period and that is similar to the u.s .", "plan previously described .", "three-year periods began in 2015 , 2014 , 2013 , allowing for the purchase of a maximum of 100000 , 300000 , and 350000 shares , respectively .", "in 2015 , 2014 , and 2013 , 2779 shares , 642 shares , and 172110 shares , respectively , were issued under the plan .", "compensation expense of $ 2 million was recognized in 2015 and 2014 , as compared to $ 1 million of compensation expense in 2013 .", "12 .", "derivatives and hedging the company is exposed to market risks , including changes in foreign currency exchange rates and interest rates .", "to manage the risk related to these exposures , the company enters into various derivative instruments that reduce these risks by creating offsetting exposures .", "the company does not enter into derivative transactions for trading or speculative purposes .", "foreign exchange risk management the company is exposed to foreign exchange risk when it earns revenues , pays expenses , or enters into monetary intercompany transfers denominated in a currency that differs from its functional currency , or other transactions that are denominated in a currency other than its functional currency .", "the company uses foreign exchange derivatives , typically forward contracts , options and cross-currency swaps , to reduce its overall exposure to the effects of currency fluctuations on cash flows .", "these exposures are hedged , on average , for less than two years .", "these derivatives are accounted for as hedges , and changes in fair value are recorded each period in other comprehensive income ( loss ) in the consolidated statements of comprehensive income .", "the company also uses foreign exchange derivatives , typically forward contracts and options to economically hedge the currency exposure of the company's global liquidity profile , including monetary assets or liabilities that are denominated in a non-functional currency of an entity , typically on a rolling 30-day basis , but may be for up to one year in the future .", "these derivatives are not accounted for as hedges , and changes in fair value are recorded each period in other income in the consolidated statements of income. ."], "table": [["", "2015", "2014", "2013"], ["aggregate intrinsic value of stock options exercised", "$ 104", "$ 61", "$ 73"], ["cash received from the exercise of stock options", "40", "38", "61"], ["tax benefit realized from the exercise of stock options", "36", "16", "15"]], "table_ori": [["", "2015", "2014", "2013"], ["Aggregate intrinsic value of stock options exercised", "$104", "$61", "$73"], ["Cash received from the exercise of stock options", "40", "38", "61"], ["Tax benefit realized from the exercise of stock options", "36", "16", "15"]]}

Question: what was the average aggregate intrinsic value of stock options exercised from 2013 to 2015
Evidence:
table_1: the aggregate intrinsic value of stock options exercised of 2015 is $ 104 ; the aggregate intrinsic value of stock options exercised of 2014 is $ 61 ; the aggregate intrinsic value of stock options exercised of 2013 is $ 73 ;
Program: add(104, 61), add(73, #0), divide(#1, const_2), add(#2, const_3), divide(#3, const_2)
Answer:
str_answer: 79.3
exe_answer: 61