.61 , and $ 41.79 and $ 42.00 , respectively . the company calculates the value of each employee stock option , estimated on the date of grant , using the black-scholes option pricing model . the weighted-average estimated fair value of employee stock options granted during 2012 , 2011 and 2010 was $ 9.60 , $ 13.25 and $ 21.43 , respectively , using the following weighted-average assumptions: .