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Accounting for Stock-Based Compensation (Tables)
6 Months Ended
Nov. 30, 2012
Accounting for Stock-Based Compensation  
Assumptions used in the Black-Scholes option pricing model to estimate the fair value of each stock option grant

 

 

 

 

Six Months Ended

 

 

 

November 30,

 

 

 

2012

 

2011

 

Risk-free interest rate

 

0.6

%

1.5

%

Expected volatility of common stock

 

51

%

46

%

Dividend yield

 

2.3

%

1.0

%

Expected option term in years

 

5.4

 

5.7