| | Purchase Options | | |||||
| | December 31, 2013 | | | December 31, 2012 | | ||
Stock price | | $ | 3.51 | | | $ | 1.60 | |
Exercise price | | $ | 8.11 | | | $ | 8.11 | |
Annual dividend yield | | | - | | | | - | |
Expected term (years) | | | 0.50 | | | | 1.50 | |
Risk-free interest rate | | | 0.10 | % | | | 0.16 | % |
Expected volatility | | | 125 | % | | | 73 | % |
Option value | | $ | 0.45 | | | $ | 0.04 | |