Merge pull request #17 from gregwinther/master

Minor changes in Black-Scholes formula

Author: mhjensen

doc/src/Projects/2020/Project5/BlackScholes/BlackScholes.do.txt

@@ -163,7 +163,7 @@ where the present value of the exercise price is
 given by
 !bt
 \begin{equation}
-    PV(E) = Ee^{-rt},
+    PV(E) = Ee^{-r(T - t)},
 \end{equation}
 !et
 furthermore we have parameters $d_1$,
@@ -179,7 +179,7 @@ furthermore we have parameters $d_1$,
 and $d_2$,
 !bt
 \begin{equation}
-    d_2 = d_1 - \sigma \sqrt{t},
+    d_2 = d_1 - \sigma \sqrt{T - t},
 \end{equation}
 !et
 while $N$ is the cumulative normal distribution function.