During the nine months ended February 29, 2020, we granted non-qualified stock options covering a total of 100,700 common shares under our stock-based compensation plans. The weighted average option price of $38.91 per share was equal to the market price of the underlying common shares at the grant date. The fair value of these stock options, based on the Black-Scholes option-pricing model, calculated at the grant date, was $10.21 per share. The calculated pre-tax stock-based compensation expense for these stock options is $1,029,000 and will be recognized on a straight-line basis over the three-year vesting period, net of any forfeitures. The following assumptions were used to value these stock options:

Dividend yield	2.42	%
Expected volatility	33.10	%
Risk-free interest rate	1.86	%
Expected term (years)	6.0

Expected volatility is based on the historical volatility of our common shares and the risk-free interest rate is based on the U.S. Treasury strip rate for the expected term of the stock options. The expected term was developed using historical exercise experience.

During the nine months ended February 29, 2020, we granted an aggregate of 244,850 service-based restricted common shares under our stock-based compensation plans. The fair value of these restricted common shares was equal to the weighted average closing market price of the underlying common shares on the respective dates of grant, or $37.60 per share. The calculated pre-tax stock-based compensation expense for these restricted common shares is $9,205,000 and will be recognized on a straight-line basis over the service-based vesting period, generally three-years, net of any forfeitures.

On September 25, 2019, we granted 50,000 restricted common shares to a key employee under one of our stock-based compensation plans. Vesting of this restricted common share award is contingent upon the price of our common shares reaching $65.00 per share and remaining at or above that price for 90 consecutive days during the five-year period following the date of grant and the completion of a five-year service vesting period. The grant-date fair value of these restricted common shares, as determined by a Monte Carlo simulation model, was $14.31 per share. The following assumptions were used to determine the grant-date fair value and the derived service period for these restricted common shares:

Dividend yield	2.69	%
Expected volatility	34.90	%
Risk-free interest rate	1.60	%

The calculated pre-tax stock-based compensation expense for these restricted common shares is $716,000 and will be recognized on a straight-line basis over the five-year service vesting period, net of any forfeitures.

We have awarded performance shares to certain key employees under our stock-based compensation plans. These performance shares are earned based on the level of achievement with respect to corporate targets for cumulative corporate economic value added, earnings per share growth and, in the case of business unit executives, business unit operating income targets for the three-year periods ending May 31, 2020, 2021 and 2022. These performance share awards will be paid, to the extent earned, in common shares of Worthington Industries, Inc. in the fiscal quarter following the end of the applicable three-year performance period. The fair values of our performance shares are determined by the closing market prices of the underlying common shares at the respective grant dates of the performance shares and the pre-tax stock-based compensation expense is based on our periodic assessment of the probability of the targets being achieved and our estimate of the number of common shares that will ultimately be issued. During the nine months ended February 29, 2020, we granted performance share awards covering an aggregate of 55,500 common shares (at target levels). The calculated pre-tax stock-based compensation expense for these performance shares is $2,160,000. The ultimate pre-tax stock-based compensation expense to be recognized over the three-year performance period will vary based on our periodic assessment of the probability of the targets being achieved.