I am trying to implement some financial formulas in Excel, and I sadly do not see an implied volatility smile, as I am being told I should. What's going on here?
If rate is zero, spot is 100, maturity is 1 year, the call price is 10, and strike ranges from 80 to 150, then I get a rising implied volatility when strike goes from 90 to 150, and for strike equal to 80 or thereabouts, I get an implied volatility of 0.999.