A Chicago-based financial institution intends to design three different currency call options. More information is provided below.

1b. What is the most important convenience pertaining to the exponential function (i.e., f(x) = exp(x))? Please explain.

\begin{tabular}{|l|l|l|l|} \hline Foreign Currency (fc) & Singaporean Dollar (SGD) & Bahraini Dinar (BHD) & Czech Koruna (CZK) \\ \hline Spot Rate (USD/fc) & 0.744 & 2.65 & 0.0453 \\ \hline Exercise Price (USD/fc) & 0.765 & 2.673 & 0.048 \\ \hline Domestic Interest Rate (\%) & 1.75 & 1.75 & 1.75 \\ \hline Foreign Interest Rate (\%) & 2 & 2.5 & 3.23 \\ \hline Time (years) & 1 & 1 & 1 \\ \hline Volatility (\% p.a.) & 3.65 & 8.25 & 12.35 \\ \hline \end{tabular}