As disclosed in Note 15, on October 6, 2017, the Company issued restricted stock awards totaling 3,900,000 shares of its common stock to 16 employees and awarded nonqualified stock options to purchase an aggregate of 360,000 shares of its common stock at a strike price of $1.98 per share to two employees. Shares of restricted stock have the same dividend and voting rights as common stock while options do not. All awards were issued at the fair value of the underlying shares at the grant date.

During the three months ended June 30, 2019, no stock options were granted. Total compensation expense related to options granted was $54 for the three months ended June 30, 2019, and $54 for the three months ended June 30, 2018. As of June 30, 2019, there was total remaining compensation expense of $274 related to stock options, which will be recorded over a weighted average period of approximately 1.27 years. During the three months ended June 30, 2019, options to purchase a total of 50,000 shares were exercised.

The Company has determined the fair value of such stock options using the Black-Scholes option valuation model based on the following key assumptions:

Stock-based compensation expense for the cost of the awards granted is based on the grant-date fair value. For stock option awards, the fair value is estimated at the date of grant using the Black-Scholes option-pricing model. This model requires the input of highly subjective assumptions, changes to which can materially affect the fair value estimate. Additionally, there may be other factors that would otherwise have a significant effect on the value of employee stock options granted but are not considered by the model. Accordingly, while management believes that the Black-Scholes option-pricing model provides a reasonable estimate of fair value, the model does not necessarily provide the best single measure of fair value for the Company’s employee stock options.

The following is a summary of stock option activity for the three months ended June 30, 2019:

During the three months ended June 30, 2019, no restricted shares were awarded. The compensation expense related to restricted stock grants was $719 during the three months ended June 30, 2019, and $784 during the three months ended June 30, 2018. As of June 30, 2019, there was $2,667 of total unrecognized compensation cost related to non-vested shares of common stock granted. The cost is expected to be recognized over a weighted average period of 1.17 years.

The table below summarizes the activity for the Company’s restricted stock outstanding during the three months ended June 30, 2019: