Notes to consolidated financial statements  September 27, 2014 and September 28, 2013 Stock option plan (Millions of dollars, unless otherwise indicated) The  Corporation has a stock option plan for certain Corporation employees providing for the grant of options to purchase  up  to 10,000,000 Common Shares. As at September 27, 2014, a balance of 2,626,052 shares could be issued following  the exercise of stock options ( 2,814,512  as at September 28, 2013 ).  The subscription price of each Common Share  under an option granted pursuant to  the  plan is equal to  the  market price  of  the shares on the day prior to option grant  date and must be paid in full at the time the option is exercised. While the Board of Directors determines other terms  and  conditions for the exercise of options, no options may have a term of more than five years from the date the option  may initially be exercised, in whole or in part, and the total term may in no circumstances exceed ten years from the  option grant date. Options may generally be exercised two years after their grant date and vest at the rate of 20% per  year .  The  outstanding  options  and  the  changes  during  the  year  were  summarized  as follows: The information regarding the stock options outstanding and exercisable as at  September 27, 2014 was summarized  as below : The weighted average fair value of $ 8.89  per option ($ 11.30  in 2013 )  for stock options granted during fiscal 2014 was  determined at the time of grant using the Black-Scholes model and the following weighted average assumptions: risk- free interest rate of 1.7 %  ( 1.2%  in 2013 ),  expected life of 5.3  years  ( 5.4  years in 2013 ),  expected volatility of 16.3 %  ( 21.0%  in 2013 )  and expected dividend yield of 1.8 %  ( 1.5%  in 2013 ).  The expected volatility is based on the historic  share  price volatility over a period similar  to  the life  of  the options. Compensation  expense  for  these options amounted to $2.2for fiscal  2014  ($2.0 in  2013 ). - 72 - Outstanding options Exercisable options Range of exercise prices (Dollars) Number  (Thousands) W eighted  average  remaining  period  (Months) W eighted  average  exercise  price (Dollars) Number  (Thousands) W eighted  average  exercise  price  (Dollars) 24.73  à 29.63  146  7.3  25.29  146  25.29 34.97  à 43.64  174  21.6  38.08  109  37.64 44.19  à 53.15  560  44.1  48.63  177  47.06 58.40  à 65.70  274  75.7  64.64  7  58.41 66.29  à 74.06  221  67.6  66.73  —  — 1,375  47.4 50.91 439 37.64 Number Weighted  average  exercise  price (Thousands)  (Dollars) Balance as at September 29, 2012  1,683 39.27 Granted 224 66.11 Exercised (445 ) 31.16 Cancelled (111 ) 42.54 Balance as at September 28, 2013  1,351 46.12 Granted 248 66.09 Exercised (189 ) 36.98 Cancelled (35 ) 48.48 Balance as at September 27, 2014  1,375 50.91