below. We use the Black-Scholes model as opposed to a lattice pricing model since employee exercise patterns, which are considered in a lattice model, are not relevant to this plan. The risk-free interest rate is based on the U.S. Treasury two-year rate in effect at the time of grant.
    Other Option Plans - Stock options are granted with an exercise price equal to the market price of the stock at the date of grant. Substantially all of the options granted are exercisable ratably over a four-year vesting period.
     The fair value of the options are estimated using a lattice option pricing model which also uses the assumptions in the table below. We believe the lattice model provides a better estimated fair value of our options as it uses a range of possible outcomes over an option term and can be adjusted for changes in certain assumptions over time. Expected volatilities are based on the historical performance of our stock. We also use historical data to estimate the timing and amount of option exercises and forfeitures within the valuation model. The expected term of the options is an output of the option pricing model and estimates the period of time that options are expected to remain unexercised. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant.
     The per share weighted-average fair value for all options granted was $6.83, $7.47 and $7.05 in 2007, 2006 and 2005, respectively. These fair values were computed using the following range of assumptions for our various stock compensation plans for the years ended November 30:

    Under our stock option plans, we may issue shares on a net basis at the request of the option holder. This occurs by netting the option cost in shares from the shares exercised.

A summary of our stock option activity for the years
ended November 30 follows:

    As of November 30, 2007, the intrinsic value (the difference between the exercise price and the market price) for options outstanding was $168.8 million and the intrinsic value for options exercisable was $161.4 million. The total intrinsic value of all options exercised during the years ended November 30, 2007 and 2006 was $33.2 million and $29.7 million, respectively. A summary of our stock options outstanding and exercisable at November 30, 2007 follows:

A summary of our RSU activity for the years ended
November 30, 2007 and 2006 follows:

No RSUs were issued in 2005.