The fair value of each option grant on the date of grant is estimated using the Black-Scholes option-pricing model.  On the date of grant, the following weighted average assumptions were utilized for options granted during the three months ended March 31, 2015 and 2014.

The following table presents information relating to all stock options outstanding and exercisable at March 31, 2015:

During the three month period ended March 31, 2015, the Company granted 5-year stock options to each of its three non-management directors to purchase 35,000 shares of its common stock at an exercise price of $2.34 per share.  Such options vest over a one year period in four equal quarterly amounts beginning on April 22, 2015, subject to continued service on the Board.

The Company recorded stock-based compensation of $100,000 and $27,000 for the three months ended March 31, 2015 and March 31, 2014, respectively.  The Company has an aggregate of $202,000 of unrecognized stock-based compensation cost as of March 31, 2015.  The aggregate intrinsic value of options exercisable at March 31, 2015 was $2,721,000.

During the three month period ended March 31, 2014, the Company’s Executive Vice President exercised a stock option to purchase 75,000 shares of the Company’s common stock at an exercise price of $0.68 per share.  The option was exercised on a net exercise (cashless) basis by delivery to the Company of 31,098 shares of common stock.  In addition, 16,968 shares were delivered to the Company with an aggregate value of $28,000 to fund payroll withholding taxes on exercise, resulting in net shares of 26,934 issued to the Company’s Executive Vice President with respect to such option exercise.

As of March 31, 2015, the following are the outstanding warrants to purchase shares of the Company's common stock:

All of the aforementioned warrants were issued to Recognition Interface, LLC in connection with the Company’s acquisition of the Mirror Worlds Patent Portfolio (see Note J[2]).