... American , pp. 9 0- 98. 19 Turning Finance into Science: Risk Management and the Black-Scholes Options Pricing Model Albert KimMary FrauleyWriting for the SciencesEnglish ENG-LBE 09Monday, ... letter) sigma , the higher the interest rate r, the longer the time until the call date t and the lower the strike price L, the higher the value of the option Cwill be.Limitations of the Model As ... (the first term) on the right- handside, and the expected cost (the second term) if the option is exercised. The higher the current share price S, the higher the volatility of the share price(Greek...