Use the following information to estimate the premium of a call option using the Black-Scholes Model So: $240 K: $250 R: 4.5% T: 18 months N(d): 0.4655 N(d2): 0.1844 You measure the standard deviation of a stock's returns at 32% and use it to estimate the Black- Scholes Call price at $42.50. Looking at actual market data, you notice the call option is actually selling for $39.88. What might explain the difference?