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.  There were no option grants during the three months ended March 31, 2016.

The following table presents information relating to all stock options outstanding and exercisable at March 31, 2016:

The Company recorded stock-based compensation of $12,000 and $100,000 for the three months ended March 31, 1016 and March 31, 2015, respectively.  The Company had no unrecognized stock-based compensation cost as of March 31, 2016.  The aggregate intrinsic value of options exercisable at March 31, 2016 was $1,551,000.

During the three month period ended March 31, 2016, the Company's Chief Financial Officer and Executive Vice President exercised stock options to purchase 100,000 shares of the Company's common stock, at an exercise price of $1.59 per share, and 240,000 shares of common stock, at an exercise price of $1.60 per share, respectively.  The options were exercised on a partial cashless (net exercise) basis by delivery to the Company of an aggregate of 249,820 shares of the Company's common stock (Chief Financial Officer – 50,857 shares and Executive Vice President - 198,963 shares) and $60,000.  In addition an aggregate of 22,655 shares (Chief Financial Officer – 5,563 shares and Executive Vice President – 17,092 shares) were delivered to fund payroll withholding taxes on exercise, resulting in net shares of 43,580 and 23,945 issued to the Chief Financial Officer and Executive Vice President, respectively, with respect to such option exercises.  In addition, during the three month period ended March 31, 2016, a consultant to the Company exercised a stock option to purchase 90,000 shares of the Company's common stock, at an exercise price of $1.60 per share.  Such option was exercised on a cashless (net exercise) basis by delivery to the Company of 72,727 shares of common stock resulting in 17,273 net shares issued to the consultant with respect to such option exercise.

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 vested over a one-year period in four equal quarterly amounts beginning on April 22, 2015, subject to continued service on the Board.

As of March 31, 2016, 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 I[2]).